Introduce Data Access MONitor (DAMON)

PATCH Superseded SeongJae Park 1 participant 18 messages May 18, 2020 – May 19, 2020

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2020-05-18 10:01 UTC #0 lore raw

v12 cover Introduce Data Access MONitor (DAMON)

From: SeongJae Park <[email protected]>

Introduction
============

DAMON is a data access monitoring framework subsystem for the Linux kernel. The core mechanisms of DAMON called 'region based sampling' and adaptive regions adjustment' (refer to :doc:mechanisms for the detail) make it accurate, efficient, and scalable. Using this framework, therefore, the kernel's core memory management mechanisms including reclamation and THP can be optimized for better memory management. The memory management optimization works that have not merged into the mainline due to their high data access monitoring overhead will be able to have another try. In user space, meanwhile, users who have some special workloads will be able to write personalized tools or applications for more understanding and specialized optimizations of their systems using the DAMON as a framework.

More Information
================

We prepared a showcase web site[1] that you can get more information of DAMON. There are

- the official documentation of DAMON[2],
- the heatmap format dynamic access pattern of various realistic workloads for heap area[3], mmap()-ed area[4], and stack[5] area,
- the dynamic working set size distribution[6] and chronological working set size changes[7], and
- the latest performance test results[8].

[1] https://damonitor.github.io
[2] https://damonitor.github.io/doc/html/latest
[3] https://damonitor.github.io/test/result/visual/latest/heatmap.0.html
[4] https://damonitor.github.io/test/result/visual/latest/heatmap.1.html
[5] https://damonitor.github.io/test/result/visual/latest/heatmap.2.html
[6] https://damonitor.github.io/test/result/visual/latest/wss_sz.html
[7] https://damonitor.github.io/test/result/visual/latest/wss_time.html
[8] https://damonitor.github.io/test/result/perf/latest/html/index.html

Evaluations
===========

We evaluated DAMON's overhead, monitoring quality and usefulness using 25 realistic workloads on my QEMU/KVM based virtual machine.

DAMON is lightweight. It consumes only 0.03% more system memory and up to 1% CPU time. It makes target worloads only 0.7% slower.

DAMON is accurate and useful for memory management optimizations. An experimental DAMON-based operation scheme for THP removes 63.12% of THP memory overheads while preserving 49.15% of THP speedup. Another experimental DAMON-based 'proactive reclamation' implementation reduces 85.85% of residentail sets and 21.98% of system memory footprint while incurring only 2.42% runtime overhead in best case (parsec3/freqmine).

NOTE that the experimentail THP optimization and proactive reclamation are not for production, just only for proof of concepts.

Please refer to 'Appendix C' for detailed evaluation setup and results.

Baseline and Complete Git Trees
===============================

The patches are based on the v5.6. You can also clone the complete git tree:

    $ git clone git://github.com/sjp38/linux -b damon/patches/v12

The web is also available:
https://github.com/sjp38/linux/releases/tag/damon/patches/v12

There are a couple of trees for entire DAMON patchset series. The first one[1] contains the changes for latest release, while the other one[2] contains the changes for next release.

[1] https://github.com/sjp38/linux/tree/damon/master
[2] https://github.com/sjp38/linux/tree/damon/next

Sequence Of Patches
===================

The patches are organized in the following sequence. The first two patches are preparation of DAMON patchset. The 1st patch adds typos found in previous versions of DAMON patchset to 'scripts/spelling.txt' so that the typos can be caught by 'checkpatch.pl'. The 2nd patch exports 'lookup_page_ext()' to GPL modules so that it can be used by DAMON even though it is built as a loadable module.

Next five patches implement the core of DAMON and it's programming interface. The 3rd patch introduces DAMON module, it's data structures, and data structure related common functions. Following four patches (4nd to 7th) implements the core mechanisms of DAMON, namely regions based sampling (patch 4), adaptive regions adjustment (patches 5-6), and dynamic memory mapping chage adoption (patch 7).

Following four patches are for low level users of DAMON. The 8th patch implements callbacks for each of monitoring steps so that users can do whatever they want with the access patterns. The 9th one implements recording of access patterns in DAMON for better convenience and efficiency. Each of next two patches (10th and 11th) respectively adds a debugfs interface for privileged people and/or programs in user space, and a tracepoint for other tracepoints supporting tracers such as perf.

Two patches for high level users of DAMON follows. To provide a minimal reference to the debugfs interface and for high level use/tests of the DAMON, the next patch (12th) implements an user space tool. The 13th patch adds a document for administrators of DAMON.

Next two patches are for tests. The 14th and 15th patches provide unit tests (based on kunit) and user space tests (based on kselftest), respectively.

Finally, the last patch (16th) updates the MAINTAINERS file.

Patch History
=============

Below are main changes for recent 5 versions of this patchset. Please refer to oldest patchset listed here to get older history.

Changes from v11
(https://lore.kernel.org/linux-mm/[email protected]/)
- Rewrite the document (Stefan Nuernberger)
- Make 'damon_for_each_*' argument order consistent (Leonard Foerster)
- Fix wrong comment in 'kdamond_merge_regions()' (Leonard Foerster)

Changes from v10
(https://lore.kernel.org/linux-mm/[email protected]/)
- Reduce aggressive split overhead by doing it only if required

Changes from v9
(https://lore.kernel.org/linux-mm/[email protected]/)
- Split each region into 4 subregions if possible (Jonathan Cameraon)
- Update kunit test for the split code change

Changes from v8
(https://lore.kernel.org/linux-mm/[email protected]/)
- Make regions always aligned by minimal region size that can be changed (Stefan Nuernberger)
- Store binary format version in the recording file (Stefan Nuernberger)
- Use 'int' for pid instead of 'unsigned long' (Stefan Nuernberger)
- Fix a race condition in damon thread termination (Stefan Nuernberger)
- Optimize random value generation and recording (Stefan Nuernberger)
- Clean up commit messages and comments (Stefan Nuernberger)
- Clean up code (Stefan Nuernberger)
- Use explicit signalling and 'do_exit()' for damon thread termination
- Add more typos to spelling.txt
- Update the performance evaluation results
- Describe future plans in the cover letter

Changes from v7
(https://lore.kernel.org/linux-mm/[email protected]/)
- Cleanup variable names (Jonathan Cameron)
- Split sampling address setup from access_check() (Jonathan Cameron)
- Make sampling address to always locate in the region (Jonathan Cameron)
- Make initial region's sampling addr to be old (Jonathan Cameron)
- Split kdamond on/off function to seperate functions (Jonathan Cameron)
- Fix wrong kernel doc comments (Jonathan Cameron)
- Reset 'last_accessed' to false in kdamond_check_access() if necessary
- Rebase on v5.6

SeongJae Park (16):
scripts/spelling: Add a few more typos mm/page_ext: Export lookup_page_ext() to GPL modules
mm: Introduce Data Access MONitor (DAMON) mm/damon: Implement region based sampling mm/damon: Adaptively adjust regions
mm/damon: Split regions into 3 subregions if necessary mm/damon: Apply dynamic memory mapping changes mm/damon: Implement callbacks
mm/damon: Implement access pattern recording mm/damon: Add debugfs interface
mm/damon: Add tracepoints
tools: Add a minimal user-space tool for DAMON Documentation/admin-guide/mm: Add a document for DAMON mm/damon: Add kunit tests
mm/damon: Add user space selftests
MAINTAINERS: Update for DAMON

 Documentation/admin-guide/mm/damon/api.rst    |    9 +
 .../admin-guide/mm/damon/damon_heatmap.png    |  Bin 0 -> 8366 bytes
 .../admin-guide/mm/damon/damon_wss_change.png |  Bin 0 -> 7211 bytes
 .../admin-guide/mm/damon/damon_wss_dist.png   |  Bin 0 -> 6173 bytes
 Documentation/admin-guide/mm/damon/faq.rst    |   39 +
 .../admin-guide/mm/damon/freqmine_heatmap.png |  Bin 0 -> 8687 bytes
 .../admin-guide/mm/damon/freqmine_wss_sz.png  |  Bin 0 -> 4986 bytes
 .../mm/damon/freqmine_wss_time.png            |  Bin 0 -> 6283 bytes
 Documentation/admin-guide/mm/damon/guide.rst  |  196 +++
 Documentation/admin-guide/mm/damon/index.rst  |   50 +
 .../admin-guide/mm/damon/mechanisms.rst       |  111 ++
 Documentation/admin-guide/mm/damon/plans.rst  |   49 +
 Documentation/admin-guide/mm/damon/start.rst  |  119 ++
 .../mm/damon/streamcluster_heatmap.png        |  Bin 0 -> 37916 bytes
 .../mm/damon/streamcluster_wss_sz.png         |  Bin 0 -> 5522 bytes
 .../mm/damon/streamcluster_wss_time.png       |  Bin 0 -> 6322 bytes
 Documentation/admin-guide/mm/damon/usage.rst  |  305 ++++
 Documentation/admin-guide/mm/index.rst        |    1 +
 Documentation/index.rst                       |  176 +-
 MAINTAINERS                                   |   12 +
 include/linux/damon.h                         |   78 +
 include/trace/events/damon.h                  |   43 +
 mm/Kconfig                                    |   23 +
 mm/Makefile                                   |    1 +
 mm/damon-test.h                               |  622 +++++++
 mm/damon.c                                    | 1511 +++++++++++++++++
 mm/page_ext.c                                 |    1 +
 scripts/spelling.txt                          |    8 +
 tools/damon/.gitignore                        |    1 +
 tools/damon/_dist.py                          |   36 +
 tools/damon/_recfile.py                       |   23 +
 tools/damon/bin2txt.py                        |   67 +
 tools/damon/damo                              |   37 +
 tools/damon/heats.py                          |  362 ++++
 tools/damon/nr_regions.py                     |   91 +
 tools/damon/record.py                         |  212 +++
 tools/damon/report.py                         |   45 +
 tools/damon/wss.py                            |   97 ++
 tools/testing/selftests/damon/Makefile        |    7 +
 .../selftests/damon/_chk_dependency.sh        |   28 +
 tools/testing/selftests/damon/_chk_record.py  |  108 ++
 .../testing/selftests/damon/debugfs_attrs.sh  |  139 ++
 .../testing/selftests/damon/debugfs_record.sh |   50 +
 43 files changed, 4489 insertions(+), 168 deletions(-)
 create mode 100644 Documentation/admin-guide/mm/damon/api.rst
 create mode 100644 Documentation/admin-guide/mm/damon/damon_heatmap.png
 create mode 100644 Documentation/admin-guide/mm/damon/damon_wss_change.png
 create mode 100644 Documentation/admin-guide/mm/damon/damon_wss_dist.png
 create mode 100644 Documentation/admin-guide/mm/damon/faq.rst
 create mode 100644 Documentation/admin-guide/mm/damon/freqmine_heatmap.png
 create mode 100644 Documentation/admin-guide/mm/damon/freqmine_wss_sz.png
 create mode 100644 Documentation/admin-guide/mm/damon/freqmine_wss_time.png
 create mode 100644 Documentation/admin-guide/mm/damon/guide.rst
 create mode 100644 Documentation/admin-guide/mm/damon/index.rst
 create mode 100644 Documentation/admin-guide/mm/damon/mechanisms.rst
 create mode 100644 Documentation/admin-guide/mm/damon/plans.rst
 create mode 100644 Documentation/admin-guide/mm/damon/start.rst
 create mode 100644 Documentation/admin-guide/mm/damon/streamcluster_heatmap.png
 create mode 100644 Documentation/admin-guide/mm/damon/streamcluster_wss_sz.png
 create mode 100644 Documentation/admin-guide/mm/damon/streamcluster_wss_time.png
 create mode 100644 Documentation/admin-guide/mm/damon/usage.rst
 create mode 100644 include/linux/damon.h
 create mode 100644 include/trace/events/damon.h
 create mode 100644 mm/damon-test.h
 create mode 100644 mm/damon.c
 create mode 100644 tools/damon/.gitignore
 create mode 100644 tools/damon/_dist.py
 create mode 100644 tools/damon/_recfile.py
 create mode 100644 tools/damon/bin2txt.py
 create mode 100755 tools/damon/damo
 create mode 100644 tools/damon/heats.py
 create mode 100644 tools/damon/nr_regions.py
 create mode 100644 tools/damon/record.py
 create mode 100644 tools/damon/report.py
 create mode 100644 tools/damon/wss.py
 create mode 100644 tools/testing/selftests/damon/Makefile
 create mode 100644 tools/testing/selftests/damon/_chk_dependency.sh
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 create mode 100755 tools/testing/selftests/damon/debugfs_attrs.sh
 create mode 100755 tools/testing/selftests/damon/debugfs_record.sh

Signature · 340 lines

2.17.1

================================== >8 =========================================
Appendix A: Related Works
=========================

There are a number of researches[1,2,3,4,5,6] optimizing memory management
mechanisms based on the actual memory access patterns that shows impressive
results.  However, most of those has no deep consideration about the monitoring
of the accesses itself.  Some of those focused on the overhead of the
monitoring, but does not consider the accuracy scalability[6] or has additional
dependencies[7].  Indeed, one recent research[5] about the proactive
reclamation has also proposed[8] to the kernel community but the monitoring
overhead was considered a main problem.

[1] Subramanya R Dulloor, Amitabha Roy, Zheguang Zhao, Narayanan Sundaram,
    Nadathur Satish, Rajesh Sankaran, Jeff Jackson, and Karsten Schwan. 2016.
    Data tiering in heterogeneous memory systems. In Proceedings of the 11th
    European Conference on Computer Systems (EuroSys). ACM, 15.
[2] Youngjin Kwon, Hangchen Yu, Simon Peter, Christopher J Rossbach, and Emmett
    Witchel. 2016. Coordinated and efficient huge page management with ingens.
    In 12th USENIX Symposium on Operating Systems Design and Implementation
    (OSDI).  705–721.
[3] Harald Servat, Antonio J Peña, Germán Llort, Estanislao Mercadal,
    HansChristian Hoppe, and Jesús Labarta. 2017. Automating the application
    data placement in hybrid memory systems. In 2017 IEEE International
    Conference on Cluster Computing (CLUSTER). IEEE, 126–136.
[4] Vlad Nitu, Boris Teabe, Alain Tchana, Canturk Isci, and Daniel Hagimont.
    2018. Welcome to zombieland: practical and energy-efficient memory
    disaggregation in a datacenter. In Proceedings of the 13th European
    Conference on Computer Systems (EuroSys). ACM, 16.
[5] Andres Lagar-Cavilla, Junwhan Ahn, Suleiman Souhlal, Neha Agarwal, Radoslaw
    Burny, Shakeel Butt, Jichuan Chang, Ashwin Chaugule, Nan Deng, Junaid
    Shahid, Greg Thelen, Kamil Adam Yurtsever, Yu Zhao, and Parthasarathy
    Ranganathan.  2019. Software-Defined Far Memory in Warehouse-Scale
    Computers.  In Proceedings of the 24th International Conference on
    Architectural Support for Programming Languages and Operating Systems
    (ASPLOS).  ACM, New York, NY, USA, 317–330.
    DOI:https://doi.org/10.1145/3297858.3304053
[6] Carl Waldspurger, Trausti Saemundsson, Irfan Ahmad, and Nohhyun Park.
    2017. Cache Modeling and Optimization using Miniature Simulations. In 2017
    USENIX Annual Technical Conference (ATC). USENIX Association, Santa
    Clara, CA, 487–498.
    https://www.usenix.org/conference/atc17/technical-sessions/
[7] Haojie Wang, Jidong Zhai, Xiongchao Tang, Bowen Yu, Xiaosong Ma, and
    Wenguang Chen. 2018. Spindle: Informed Memory Access Monitoring. In 2018
    USENIX Annual Technical Conference (ATC). USENIX Association, Boston, MA,
    561–574.  https://www.usenix.org/conference/atc18/presentation/wang-haojie
[8] Jonathan Corbet. 2019. Proactively reclaiming idle memory. (2019).
    https://lwn.net/Articles/787611/.


Appendix B: Limitations of Other Access Monitoring Techniques
=============================================================

The memory access instrumentation techniques which are applied to
many tools such as Intel PIN is essential for correctness required cases such
as memory access bug detections or cache level optimizations.  However, those
usually incur exceptionally high overhead which is unacceptable.

Periodic access checks based on access counting features (e.g., PTE Accessed
bits or PG_Idle flags) can reduce the overhead.  It sacrifies some of the
quality but it's still ok to many of this domain.  However, the overhead
arbitrarily increase as the size of the target workload grows.  Miniature-like
static region based sampling can set the upperbound of the overhead, but it
will now decrease the quality of the output as the size of the workload grows.

DAMON is another solution that overcomes the limitations.  It is 1) accurate
enough for this domain, 2) light-weight so that it can be applied online, and
3) allow users to set the upper-bound of the overhead, regardless of the size
of target workloads.  It is implemented as a simple and small kernel module to
support various users in both of the user space and the kernel space.  Refer to
'Evaluations' section below for detailed performance of DAMON.

For the goals, DAMON utilizes its two core mechanisms, which allows lightweight
overhead and high quality of output, repectively.  To show how DAMON promises
those, refer to 'Mechanisms of DAMON' section below.


Appendix C: Evaluations
=======================

Setup
-----

On my personal QEMU/KVM based virtual machine on an Intel i7 host machine
running Ubuntu 18.04, I measure runtime and consumed system memory while
running various realistic workloads with several configurations.  I use 13 and
12 workloads in PARSEC3[3] and SPLASH-2X[4] benchmark suites, respectively.  I
personally use another wrapper scripts[5] for setup and run of the workloads.
On top of this patchset, we also applied the DAMON-based operation schemes
patchset[6] for this evaluation.

Measurement
~~~~~~~~~~~

For the measurement of the amount of consumed memory in system global scope, I
drop caches before starting each of the workloads and monitor 'MemFree' in the
'/proc/meminfo' file.  To make results more stable, I repeat the runs 5 times
and average results.  You can get stdev, min, and max of the numbers among the
repeated runs in appendix below.

Configurations
~~~~~~~~~~~~~~

The configurations I use are as below.

orig: Linux v5.5 with 'madvise' THP policy
rec: 'orig' plus DAMON running with record feature
thp: same with 'orig', but use 'always' THP policy
ethp: 'orig' plus a DAMON operation scheme[6], 'efficient THP'
prcl: 'orig' plus a DAMON operation scheme, 'proactive reclaim[7]'

I use 'rec' for measurement of DAMON overheads to target workloads and system
memory.  The remaining configs including 'thp', 'ethp', and 'prcl' are for
measurement of DAMON monitoring accuracy.

'ethp' and 'prcl' is simple DAMON-based operation schemes developed for
proof of concepts of DAMON.  'ethp' reduces memory space waste of THP by using
DAMON for decision of promotions and demotion for huge pages, while 'prcl' is
as similar as the original work.  Those are implemented as below:

# format: <min/max size> <min/max frequency (0-100)> <min/max age> <action>
# ethp: Use huge pages if a region >2MB shows >5% access rate, use regular
# pages if a region >2MB shows <5% access rate for >1 second
2M null    5 null    null null    hugepage
2M null    null 5    1s null      nohugepage

# prcl: If a region >4KB shows <5% access rate for >5 seconds, page out.
4K null    null 5    500ms null      pageout

Note that both 'ethp' and 'prcl' are designed with my only straightforward
intuition, because those are for only proof of concepts and monitoring accuracy
of DAMON.  In other words, those are not for production.  For production use,
those should be tuned more.


[1] "Redis latency problems troubleshooting", https://redis.io/topics/latency
[2] "Disable Transparent Huge Pages (THP)",
    https://docs.mongodb.com/manual/tutorial/transparent-huge-pages/
[3] "The PARSEC Becnhmark Suite", https://parsec.cs.princeton.edu/index.htm
[4] "SPLASH-2x", https://parsec.cs.princeton.edu/parsec3-doc.htm#splash2x
[5] "parsec3_on_ubuntu", https://github.com/sjp38/parsec3_on_ubuntu
[6] "[RFC v4 0/7] Implement Data Access Monitoring-based Memory Operation
    Schemes",
    https://lore.kernel.org/linux-mm/[email protected]/
[7] "Proactively reclaiming idle memory", https://lwn.net/Articles/787611/


Results
-------

Below two tables show the measurement results.  The runtimes are in seconds
while the memory usages are in KiB.  Each configurations except 'orig' shows
its overhead relative to 'orig' in percent within parenthesises.

runtime                 orig     rec      (overhead) thp      (overhead) ethp     (overhead) prcl     (overhead)
parsec3/blackscholes    107.065  107.478  (0.39)     106.682  (-0.36)    107.365  (0.28)     111.811  (4.43)
parsec3/bodytrack       79.256   79.450   (0.25)     78.645   (-0.77)    79.314   (0.07)     80.305   (1.32)
parsec3/canneal         139.497  141.181  (1.21)     121.526  (-12.88)   130.074  (-6.75)    154.644  (10.86)
parsec3/dedup           11.879   11.873   (-0.05)    11.693   (-1.56)    11.948   (0.58)     12.694   (6.86)
parsec3/facesim         207.814  208.467  (0.31)     203.743  (-1.96)    206.759  (-0.51)    214.603  (3.27)
parsec3/ferret          190.124  190.955  (0.44)     189.575  (-0.29)    190.852  (0.38)     191.548  (0.75)
parsec3/fluidanimate    211.046  212.282  (0.59)     208.832  (-1.05)    212.143  (0.52)     218.774  (3.66)
parsec3/freqmine        289.259  290.096  (0.29)     288.510  (-0.26)    290.177  (0.32)     296.269  (2.42)
parsec3/raytrace        118.522  119.701  (0.99)     119.469  (0.80)     118.964  (0.37)     130.584  (10.18)
parsec3/streamcluster   323.619  327.830  (1.30)     283.374  (-12.44)   287.837  (-11.06)   330.216  (2.04)
parsec3/swaptions       154.007  155.714  (1.11)     154.767  (0.49)     154.955  (0.62)     155.256  (0.81)
parsec3/vips            58.822   58.750   (-0.12)    58.564   (-0.44)    58.807   (-0.02)    60.320   (2.55)
parsec3/x264            67.335   72.516   (7.69)     64.680   (-3.94)    70.096   (4.10)     72.465   (7.62)
splash2x/barnes         80.335   80.979   (0.80)     73.758   (-8.19)    78.874   (-1.82)    99.226   (23.52)
splash2x/fft            33.441   33.312   (-0.38)    22.909   (-31.49)   31.561   (-5.62)    41.496   (24.09)
splash2x/lu_cb          85.691   85.706   (0.02)     84.352   (-1.56)    85.943   (0.29)     88.914   (3.76)
splash2x/lu_ncb         92.338   92.749   (0.45)     89.773   (-2.78)    92.888   (0.60)     94.104   (1.91)
splash2x/ocean_cp       44.542   44.795   (0.57)     42.958   (-3.56)    44.061   (-1.08)    49.091   (10.21)
splash2x/ocean_ncp      82.101   82.006   (-0.12)    51.418   (-37.37)   64.496   (-21.44)   105.998  (29.11)
splash2x/radiosity      91.296   91.353   (0.06)     90.668   (-0.69)    91.379   (0.09)     103.265  (13.11)
splash2x/radix          31.243   31.417   (0.56)     25.176   (-19.42)   30.297   (-3.03)    38.474   (23.14)
splash2x/raytrace       84.405   84.863   (0.54)     83.498   (-1.08)    83.637   (-0.91)    85.166   (0.90)
splash2x/volrend        87.516   88.156   (0.73)     86.311   (-1.38)    87.016   (-0.57)    88.318   (0.92)
splash2x/water_nsquared 233.515  233.826  (0.13)     221.169  (-5.29)    224.430  (-3.89)    236.929  (1.46)
splash2x/water_spatial  89.207   89.448   (0.27)     89.396   (0.21)     89.826   (0.69)     97.700   (9.52)
total                   2993.890 3014.920 (0.70)     2851.460 (-4.76)    2923.710 (-2.34)    3158.180 (5.49)


memused.avg             orig         rec          (overhead) thp          (overhead) ethp         (overhead) prcl         (overhead)
parsec3/blackscholes    1819997.200  1832626.000  (0.69)     1821707.000  (0.09)     1830010.400  (0.55)     1651016.200  (-9.28)
parsec3/bodytrack       1416437.600  1430462.200  (0.99)     1420736.400  (0.30)     1428355.600  (0.84)     1430327.000  (0.98)
parsec3/canneal         1040414.400  1050736.800  (0.99)     1041515.600  (0.11)     1048562.200  (0.78)     1049049.400  (0.83)
parsec3/dedup           2414431.800  2454260.400  (1.65)     2423175.400  (0.36)     2396560.200  (-0.74)    2379898.200  (-1.43)
parsec3/facesim         540432.200   551410.200   (2.03)     545978.200   (1.03)     558558.400   (3.35)     483755.400   (-10.49)
parsec3/ferret          318728.600   333971.800   (4.78)     322158.200   (1.08)     332889.200   (4.44)     327896.400   (2.88)
parsec3/fluidanimate    576917.800   585126.600   (1.42)     575123.200   (-0.31)    585429.200   (1.48)     484810.600   (-15.97)
parsec3/freqmine        987882.200   997030.600   (0.93)     990429.200   (0.26)     998484.000   (1.07)     770740.200   (-21.98)
parsec3/raytrace        1747059.800  1752904.000  (0.33)     1738853.600  (-0.47)    1753948.600  (0.39)     1578118.000  (-9.67)
parsec3/streamcluster   121857.600   133934.400   (9.91)     121777.800   (-0.07)    133145.800   (9.26)     131512.800   (7.92)
parsec3/swaptions       14123.000    29254.400    (107.14)   14017.200    (-0.75)    26470.600    (87.43)    28429.800    (101.30)
parsec3/vips            2957631.800  2972884.400  (0.52)     2938855.400  (-0.63)    2960746.000  (0.11)     2946850.800  (-0.36)
parsec3/x264            3184777.200  3214527.400  (0.93)     3177061.000  (-0.24)    3192446.600  (0.24)     3185851.800  (0.03)
splash2x/barnes         1209737.200  1214763.200  (0.42)     1242138.400  (2.68)     1215857.600  (0.51)     994280.800   (-17.81)
splash2x/fft            9362799.400  9178844.600  (-1.96)    9264052.600  (-1.05)    9164996.600  (-2.11)    9452048.200  (0.95)
splash2x/lu_cb          515716.000   524071.600   (1.62)     521226.200   (1.07)     524261.400   (1.66)     372910.200   (-27.69)
splash2x/lu_ncb         512898.200   523057.600   (1.98)     520630.800   (1.51)     523779.000   (2.12)     446282.400   (-12.99)
splash2x/ocean_cp       3346038.000  3288703.600  (-1.71)    3386906.600  (1.22)     3330937.200  (-0.45)    3266442.400  (-2.38)
splash2x/ocean_ncp      3886945.600  3871894.000  (-0.39)    7066192.000  (81.79)    5065229.800  (30.31)    3652078.200  (-6.04)
splash2x/radiosity      1467107.200  1468850.800  (0.12)     1481292.600  (0.97)     1470335.800  (0.22)     530923.400   (-63.81)
splash2x/radix          1708330.800  1699792.200  (-0.50)    1352708.600  (-20.82)   1601339.200  (-6.26)    2043947.800  (19.65)
splash2x/raytrace       44817.200    59047.800    (31.75)    52010.200    (16.05)    60407.200    (34.79)    53916.400    (20.30)
splash2x/volrend        151534.200   167791.400   (10.73)    151759.000   (0.15)     165012.400   (8.89)     160864.600   (6.16)
splash2x/water_nsquared 46549.400    61846.800    (32.86)    51741.200    (11.15)    59214.400    (27.21)    91869.400    (97.36)
splash2x/water_spatial  669085.200   675929.200   (1.02)     665924.600   (-0.47)    676218.200   (1.07)     538430.200   (-19.53)
total                   40062200.000 40073700.000 (0.03)     42888000.000 (7.05)     41103100.000 (2.60)     38052200.000 (-5.02)


DAMON Overheads
~~~~~~~~~~~~~~~

In total, DAMON recording feature incurs 0.70% runtime overhead and 0.03%
memory space overhead.

For convenience test run of 'rec', I use a Python wrapper.  The wrapper
constantly consumes about 10-15MB of memory.  This becomes high memory overhead
if the target workload has small memory footprint.  Nonetheless, the overheads
are not from DAMON, but from the wrapper, and thus should be ignored.  This
fake memory overhead continues in 'ethp' and 'prcl', as those configurations
are also using the Python wrapper.


Efficient THP
~~~~~~~~~~~~~

THP 'always' enabled policy achieves 4.76% speedup but incurs 7.05% memory
overhead.  It achieves 37.37% speedup in best case, but 81.79% memory overhead
in worst case.  Interestingly, both the best and worst case are with
'splash2x/ocean_ncp').

The 2-lines implementation of data access monitoring based THP version ('ethp')
shows 2.34% speedup and 2.60% memory overhead.  In other words, 'ethp' removes
63.12% of THP memory waste while preserving 49.15% of THP speedup in total.  In
case of the 'splash2x/ocean_ncp', 'ethp' removes 62.94% of THP memory waste
while preserving 57.37% of THP speedup.


Proactive Reclamation
~~~~~~~~~~~~~~~~~~~~

As same to the original work, I use 'zram' swap device for this configuration.

In total, our 1 line implementation of Proactive Reclamation, 'prcl', incurred
8.41% runtime overhead in total while achieving 5.83% system memory usage
reduction.

Nonetheless, as the memory usage is calculated with 'MemFree' in
'/proc/meminfo', it contains the SwapCached pages.  As the swapcached pages can
be easily evicted, I also measured the residential set size of the workloads:

rss.avg                 orig         rec          (overhead) thp          (overhead) ethp         (overhead) prcl         (overhead)
parsec3/blackscholes    591452.000   591466.400   (0.00)     593145.200   (0.29)     590609.400   (-0.14)    324379.000   (-45.16)
parsec3/bodytrack       32458.600    32352.200    (-0.33)    32218.400    (-0.74)    32376.400    (-0.25)    27186.000    (-16.24)
parsec3/canneal         841311.600   839888.400   (-0.17)    837008.400   (-0.51)    837811.000   (-0.42)    823276.200   (-2.14)
parsec3/dedup           1219096.600  1228038.800  (0.73)     1235610.800  (1.35)     1214267.000  (-0.40)    992031.000   (-18.63)
parsec3/facesim         311322.200   311574.400   (0.08)     316277.000   (1.59)     312593.800   (0.41)     188789.400   (-39.36)
parsec3/ferret          99536.600    99556.800    (0.02)     102366.000   (2.84)     99799.000    (0.26)     88392.000    (-11.20)
parsec3/fluidanimate    531893.600   531856.000   (-0.01)    532143.400   (0.05)     532190.200   (0.06)     421798.800   (-20.70)
parsec3/freqmine        553533.200   552730.400   (-0.15)    555642.600   (0.38)     553895.400   (0.07)     78335.000    (-85.85)
parsec3/raytrace        894094.200   894849.000   (0.08)     889964.000   (-0.46)    892865.000   (-0.14)    332911.800   (-62.77)
parsec3/streamcluster   110938.000   110968.200   (0.03)     111673.400   (0.66)     111312.200   (0.34)     109911.200   (-0.93)
parsec3/swaptions       5630.000     5634.800     (0.09)     5656.600     (0.47)     5692.000     (1.10)     4028.400     (-28.45)
parsec3/vips            32107.000    32045.200    (-0.19)    32207.800    (0.31)     32293.800    (0.58)     29093.600    (-9.39)
parsec3/x264            81926.000    82143.000    (0.26)     83258.400    (1.63)     82570.600    (0.79)     80651.800    (-1.56)
splash2x/barnes         1215468.800  1217889.800  (0.20)     1222006.800  (0.54)     1217425.600  (0.16)     752405.200   (-38.10)
splash2x/fft            9584734.800  9568872.800  (-0.17)    9660321.400  (0.79)     9646012.000  (0.64)     8367492.800  (-12.70)
splash2x/lu_cb          510555.400   510807.400   (0.05)     514448.600   (0.76)     509281.800   (-0.25)    349272.200   (-31.59)
splash2x/lu_ncb         510310.000   508915.600   (-0.27)    513886.000   (0.70)     510288.400   (-0.00)    431521.800   (-15.44)
splash2x/ocean_cp       3408724.400  3408424.600  (-0.01)    3446054.400  (1.10)     3419536.200  (0.32)     3173818.600  (-6.89)
splash2x/ocean_ncp      3923539.600  3922605.400  (-0.02)    7175526.600  (82.88)    5152558.800  (31.32)    3475756.000  (-11.41)
splash2x/radiosity      1476050.000  1475470.400  (-0.04)    1485747.000  (0.66)     1476232.600  (0.01)     269512.200   (-81.74)
splash2x/radix          1756385.400  1752676.000  (-0.21)    1431621.600  (-18.49)   1711460.800  (-2.56)    1923448.200  (9.51)
splash2x/raytrace       23286.400    23311.200    (0.11)     28440.800    (22.13)    26977.200    (15.85)    15685.200    (-32.64)
splash2x/volrend        44089.400    44125.600    (0.08)     44436.600    (0.79)     44250.400    (0.37)     27616.800    (-37.36)
splash2x/water_nsquared 29437.600    29403.200    (-0.12)    29817.400    (1.29)     30040.000    (2.05)     25369.600    (-13.82)
splash2x/water_spatial  656264.400   656566.400   (0.05)     656016.400   (-0.04)    656420.200   (0.02)     474480.400   (-27.70)
total                   28444100.000 28432200.000 (-0.04)    31535300.000 (10.87)    29698900.000 (4.41)     22787200.000 (-19.89)

In total, 19.89% of residential sets were reduced.

With parsec3/freqmine, 'prcl' reduced 85.85% of residential sets and 21.98% of
system memory usage while incurring only 2.42% runtime overhead.


Appendix D: Prototype Evaluations
=================================

A prototype of DAMON has evaluated on an Intel Xeon E7-8837 machine using 20
benchmarks that picked from SPEC CPU 2006, NAS, Tensorflow Benchmark,
SPLASH-2X, and PARSEC 3 benchmark suite.  Nonethless, this section provides
only summary of the results.  For more detail, please refer to the slides used
for the introduction of DAMON at the Linux Plumbers Conference 2019[1] or the
MIDDLEWARE'19 industrial track paper[2].

[1] SeongJae Park, Tracing Data Access Pattern with Bounded Overhead and
    Best-effort Accuracy. In The Linux Kernel Summit, September 2019.
    https://linuxplumbersconf.org/event/4/contributions/548/
[2] SeongJae Park, Yunjae Lee, Heon Y. Yeom, Profiling Dynamic Data Access
    Patterns with Controlled Overhead and Quality. In 20th ACM/IFIP
    International Middleware Conference Industry, December 2019.
    https://dl.acm.org/doi/10.1145/3366626.3368125


Quality
-------

We first traced and visualized the data access pattern of each workload.  We
were able to confirm that the visualized results are reasonably accurate by
manually comparing those with the source code of the workloads.

To see the usefulness of the monitoring, we optimized 9 memory intensive
workloads among them for memory pressure situations using the DAMON outputs.
In detail, we identified frequently accessed memory regions in each workload
based on the DAMON results and protected them with ``mlock()`` system calls by
manually modifying the source code.  The optimized versions consistently show
speedup (2.55x in best case, 1.65x in average) under artificial memory
pressures.  We use cgroups for the pressure.


Overhead
--------

We also measured the overhead of DAMON.  The upperbound we set was kept as
expected.  Besides, it was much lower (0.6 percent of the bound in best case,
13.288 percent of the bound in average).  This reduction of the overhead is
mainly resulted from its core mechanism called adaptive regions adjustment.
Refer to 'Appendix D' for more detail about the mechanism.  We also compared
the overhead of DAMON with that of a straightforward periodic PTE Accessed bit
checking based monitoring.  DAMON's overhead was smaller than it by 94,242.42x
in best case, 3,159.61x in average.

The latest version of DAMON running with its default configuration consumes
only up to 1% of CPU time when applied to realistic workloads in PARSEC3 and
SPLASH-2X and makes no visible slowdown to the target processes.

SeongJae Park

author

2020-05-18 10:01 UTC #1 lore raw

PATCH v12 1/16 scripts/spelling: Add a few more typos

From: SeongJae Park <[email protected]>

This commit adds typos found from DAMON patchset.

Signed-off-by SeongJae Park <[email protected]>

---
 scripts/spelling.txt | 8 ++++++++
 1 file changed, 8 insertions(+)

scripts/spelling.txt +8 -0

index ffa838f3a2b5..a8214d8e8e4b 100644
@@ -59,6 +59,7 @@ actualy||actually
 acumulating||accumulating
 acumulative||accumulative
 acumulator||accumulator
+acutally||actually
 adapater||adapter
 addional||additional
 additionaly||additionally

@@ -245,6 +246,7 @@ calescing||coalescing
 calle||called
 callibration||calibration
 callled||called
+callser||caller
 calucate||calculate
 calulate||calculate
 cancelation||cancellation

@@ -664,6 +666,7 @@ hanlde||handle
 hanled||handled
 happend||happened
 harware||hardware
+havind||having
 heirarchically||hierarchically
 helpfull||helpful
 hexdecimal||hexadecimal

@@ -835,6 +838,7 @@ logile||logfile
 loobpack||loopback
 loosing||losing
 losted||lost
+maangement||management
 machinary||machinery
 maibox||mailbox
 maintainance||maintenance

@@ -999,6 +1003,7 @@ partiton||partition
 pased||passed
 passin||passing
 pathes||paths
+pattrns||patterns
 pecularities||peculiarities
 peformance||performance
 peforming||performing

@@ -1238,6 +1243,7 @@ shoule||should
 shrinked||shrunk
 siginificantly||significantly
 signabl||signal
+significanly||significantly
 similary||similarly
 similiar||similar
 simlar||similar

@@ -1352,6 +1358,7 @@ thead||thread
 therfore||therefore
 thier||their
 threds||threads
+threee||three
 threshhold||threshold
 thresold||threshold
 throught||through

@@ -1391,6 +1398,7 @@ tyep||type
 udpate||update
 uesd||used
 uknown||unknown
+usccess||success
 usupported||unsupported
 uncommited||uncommitted
 unconditionaly||unconditionally

Signature · 1 line

2.17.1

SeongJae Park

author

2020-05-18 10:01 UTC #2 lore raw

PATCH v12 2/16 mm/page_ext: Export lookup_page_ext() to GPL modules

In reply to SeongJae Park

From: SeongJae Park <[email protected]>

This commit exports 'lookup_page_ext()' to GPL modules. This will be used by DAMON.

Signed-off-by SeongJae Park <[email protected]>

---
 mm/page_ext.c | 1 +
 1 file changed, 1 insertion(+)

mm/page_ext.c +1 -0

index 4ade843ff588..71169b45bba9 100644
@@ -131,6 +131,7 @@ struct page_ext *lookup_page_ext(const struct page *page)
 					MAX_ORDER_NR_PAGES);
 	return get_entry(base, index);
 }
+EXPORT_SYMBOL_GPL(lookup_page_ext);
 
 static int __init alloc_node_page_ext(int nid)
 {

Signature · 1 line

2.17.1

SeongJae Park

author

2020-05-18 10:03 UTC #3 lore raw

PATCH v12 3/16 mm: Introduce Data Access MONitor (DAMON)

In reply to SeongJae Park

From: SeongJae Park <[email protected]>

This commit introduces a kernel module named DAMON. Note that this commit is implementing only the stub for the module load/unload, basic data structures, and simple manipulation functions of the structures to keep the size of commit small. The core mechanisms of DAMON will be implemented one by one by following commits.

Signed-off-by SeongJae Park <[email protected]>

---
 include/linux/damon.h |  36 +++++++++
 mm/Kconfig            |  12 +++
 mm/Makefile           |   1 +
 mm/damon.c            | 173 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 222 insertions(+)
 create mode 100644 include/linux/damon.h
 create mode 100644 mm/damon.c

include/linux/damon.h new file +36 -0

new file mode 100644
index 000000000000..19f411d36c0d
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * DAMON api
+ *
+ * Copyright 2019-2020 Amazon.com, Inc. or its affiliates.
+ *
+ * Author: SeongJae Park <[email protected]>
+ */
+
+#ifndef _DAMON_H_
+#define _DAMON_H_
+
+#include <linux/random.h>
+#include <linux/types.h>
+
+/* Represents a monitoring target region of [vm_start, vm_end) */
+struct damon_region {
+	unsigned long vm_start;
+	unsigned long vm_end;
+	unsigned long sampling_addr;
+	unsigned int nr_accesses;
+	struct list_head list;
+};
+
+/* Represents a monitoring target task */
+struct damon_task {
+	int pid;
+	struct list_head regions_list;
+	struct list_head list;
+};
+
+struct damon_ctx {
+	struct list_head tasks_list;	/* 'damon_task' objects */
+};
+
+#endif

mm/Kconfig +12 -0

index ab80933be65f..9ea49633a6df 100644
@@ -739,4 +739,16 @@ config ARCH_HAS_HUGEPD
 config MAPPING_DIRTY_HELPERS
         bool
 
+config DAMON
+	tristate "Data Access Monitor"
+	depends on MMU
+	help
+	  Provides data access monitoring.
+
+	  DAMON is a kernel module that allows users to monitor the actual
+	  memory access pattern of specific user-space processes.  It aims to
+	  be 1) accurate enough to be useful for performance-centric domains,
+	  and 2) sufficiently light-weight so that it can be applied online.
+	  If unsure, say N.
+
 endmenu

mm/Makefile +1 -0

index 272e66039e70..5346314edee6 100644
@@ -110,3 +110,4 @@ obj-$(CONFIG_HMM_MIRROR) += hmm.o
 obj-$(CONFIG_MEMFD_CREATE) += memfd.o
 obj-$(CONFIG_MAPPING_DIRTY_HELPERS) += mapping_dirty_helpers.o
 obj-$(CONFIG_PTDUMP_CORE) += ptdump.o
+obj-$(CONFIG_DAMON) += damon.o

mm/damon.c new file +173 -0

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Signature · 1 line

2.17.1

SeongJae Park

author

2020-05-18 10:03 UTC #4 lore raw

PATCH v12 4/16 mm/damon: Implement region based sampling

In reply to SeongJae Park

From: SeongJae Park <[email protected]>

This commit implements DAMON's basic access check and region based sampling mechanisms. This change would seems make no sense, mainly because it is only a part of the DAMON's logics. Following two commits will make more sense.

Basic Access Check
------------------

DAMON basically reports what pages are how frequently accessed. Note that the frequency is not an absolute number of accesses, but a relative frequency among the pages of the target workloads.

Users can control the resolution of the reports by setting two time intervals, ``sampling interval`` and ``aggregation interval``. In detail, DAMON checks access to each page per ``sampling interval``, aggregates the results (counts the number of the accesses to each page), and reports the aggregated results per ``aggregation interval``. For the access check of each page, DAMON uses the Accessed bits of PTEs.

This is thus similar to common periodic access checks based access tracking mechanisms, which overhead is increasing as the size of the target process grows.

Region Based Sampling
---------------------

To avoid the unbounded increase of the overhead, DAMON groups a number of adjacent pages that assumed to have same access frequencies into a region. As long as the assumption (pages in a region have same access frequencies) is kept, only one page in the region is required to be checked. Thus, for each ``sampling interval``, DAMON randomly picks one page in each region and clears its Accessed bit. After one more ``sampling interval``, DAMON reads the Accessed bit of the page and increases the access frequency of the region if the bit has set meanwhile. Therefore, the monitoring overhead is controllable by setting the number of regions.

Nonetheless, this scheme cannot preserve the quality of the output if the assumption is not kept. Following commit will introduce how we can make the guarantee with best effort.

Signed-off-by SeongJae Park <[email protected]>

---
 include/linux/damon.h |  25 ++
 mm/damon.c            | 597 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 622 insertions(+)

include/linux/damon.h +25 -0

index 19f411d36c0d..558dd6ae0afa 100644
@@ -11,6 +11,8 @@
 #define _DAMON_H_
 
 #include <linux/random.h>
+#include <linux/mutex.h>
+#include <linux/time64.h>
 #include <linux/types.h>
 
 /* Represents a monitoring target region of [vm_start, vm_end) */

@@ -29,8 +31,31 @@ struct damon_task {
 	struct list_head list;
 };
 
+/*
+ * For each 'sample_interval', DAMON checks whether each region is accessed or
+ * not.  It aggregates and keeps the access information (number of accesses to
+ * each region) for each 'aggr_interval' time.
+ *
+ * All time intervals are in micro-seconds.
+ */
 struct damon_ctx {
+	unsigned long sample_interval;
+	unsigned long aggr_interval;
+	unsigned long min_nr_regions;
+
+	struct timespec64 last_aggregation;
+
+	struct task_struct *kdamond;
+	bool kdamond_stop;
+	struct mutex kdamond_lock;
+
 	struct list_head tasks_list;	/* 'damon_task' objects */
 };
 
+int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids);
+int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
+		unsigned long aggr_int, unsigned long min_nr_reg);
+int damon_start(struct damon_ctx *ctx);
+int damon_stop(struct damon_ctx *ctx);
+
 #endif

mm/damon.c +597 -0

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Signature · 1 line

2.17.1

SeongJae Park

author

2020-05-18 10:04 UTC #5 lore raw

PATCH v12 5/16 mm/damon: Adaptively adjust regions

In reply to SeongJae Park

From: SeongJae Park <[email protected]>

At the beginning of the monitoring, DAMON constructs the initial regions by evenly splitting the memory mapped address space of the process into the user-specified minimal number of regions. In this initial state, the assumption of the regions (pages in same region have similar access frequencies) is normally not kept and thus the monitoring quality could be low. To keep the assumption as much as possible, DAMON adaptively merges and splits each region.

For each ``aggregation interval``, it compares the access frequencies of adjacent regions and merges those if the frequency difference is small. Then, after it reports and clears the aggregated access frequency of each region, it splits each region into two regions if the total number of regions is smaller than the half of the user-specified maximum number of regions.

In this way, DAMON provides its best-effort quality and minimal overhead while keeping the bounds users set for their trade-off.

Signed-off-by SeongJae Park <[email protected]>

---
 include/linux/damon.h |   6 +-
 mm/damon.c            | 158 +++++++++++++++++++++++++++++++++++++++---
 2 files changed, 152 insertions(+), 12 deletions(-)

include/linux/damon.h +4 -2

index 558dd6ae0afa..f1c3f491fc50 100644
@@ -42,6 +42,7 @@ struct damon_ctx {
 	unsigned long sample_interval;
 	unsigned long aggr_interval;
 	unsigned long min_nr_regions;
+	unsigned long max_nr_regions;
 
 	struct timespec64 last_aggregation;

@@ -53,8 +54,9 @@ struct damon_ctx {
 };
 
 int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids);
-int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
-		unsigned long aggr_int, unsigned long min_nr_reg);
+int damon_set_attrs(struct damon_ctx *ctx,
+		unsigned long sample_int, unsigned long aggr_int,
+		unsigned long min_nr_reg, unsigned long max_nr_reg);
 int damon_start(struct damon_ctx *ctx);
 int damon_stop(struct damon_ctx *ctx);

mm/damon.c +148 ~~-10~~

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Signature · 1 line

2.17.1

SeongJae Park

author

2020-05-18 10:05 UTC #6 lore raw

PATCH v12 6/16 mm/damon: Split regions into 3 subregions if necessary

In reply to SeongJae Park

From: SeongJae Park <[email protected]>

Suppose that there are a very wide and cold region and a hot region, and both regions are identified by DAMON. And then, the middle small region inside the very wide and cold region becomes hot. DAMON will not be able to identify this new region because the adaptive regions adjustment mechanism splits each region to only two subregions.

This commit modifies the logic to split each region to 3 subregions if such corner case is detected.

Signed-off-by SeongJae Park <[email protected]>

---
 mm/damon.c | 51 ++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 34 insertions(+), 17 deletions(-)

mm/damon.c +34 ~~-17~~

index 6c9581104caf..bbd5b1d921da 100644
@@ -650,26 +650,32 @@ static void damon_split_region_at(struct damon_ctx *ctx,
 	damon_insert_region(new, r, damon_next_region(r));
 }
 
-/* Split every region in the given task into two randomly-sized regions */
-static void damon_split_regions_of(struct damon_ctx *ctx, struct damon_task *t)
+/* Split every region in the given task into 'nr_subs' regions */
+static void damon_split_regions_of(struct damon_ctx *ctx,
+				     struct damon_task *t, int nr_subs)
 {
 	struct damon_region *r, *next;
-	unsigned long sz_orig_region, sz_left_region;
+	unsigned long sz_region, sz_sub = 0;
+	int i;
 
 	damon_for_each_region_safe(r, next, t) {
-		sz_orig_region = r->vm_end - r->vm_start;
-
-		/*
-		 * Randomly select size of left sub-region to be at least
-		 * 10 percent and at most 90% of original region
-		 */
-		sz_left_region = ALIGN_DOWN(damon_rand(1, 10) * sz_orig_region
-					    / 10, MIN_REGION);
-		/* Do not allow blank region */
-		if (sz_left_region == 0 || sz_left_region >= sz_orig_region)
-			continue;
-
-		damon_split_region_at(ctx, r, sz_left_region);
+		sz_region = r->vm_end - r->vm_start;
+
+		for (i = 0; i < nr_subs - 1 &&
+				sz_region > 2 * MIN_REGION; i++) {
+			/*
+			 * Randomly select size of left sub-region to be at
+			 * least 10 percent and at most 90% of original region
+			 */
+			sz_sub = ALIGN_DOWN(damon_rand(1, 10) *
+					sz_region / 10, MIN_REGION);
+			/* Do not allow blank region */
+			if (sz_sub == 0 || sz_sub >= sz_region)
+				continue;
+
+			damon_split_region_at(ctx, r, sz_sub);
+			sz_region = sz_sub;
+		}
 	}
 }

@@ -687,14 +693,25 @@ static void kdamond_split_regions(struct damon_ctx *ctx)
 {
 	struct damon_task *t;
 	unsigned int nr_regions = 0;
+	static unsigned int last_nr_regions;
+	int nr_subregions = 2;
 
 	damon_for_each_task(t, ctx)
 		nr_regions += nr_damon_regions(t);
+
 	if (nr_regions > ctx->max_nr_regions / 2)
 		return;
 
+	/* If number of regions is not changed, we are maybe in corner case */
+	if (last_nr_regions == nr_regions &&
+			nr_regions < ctx->max_nr_regions / 3)
+		nr_subregions = 3;
+
 	damon_for_each_task(t, ctx)
-		damon_split_regions_of(ctx, t);
+		damon_split_regions_of(ctx, t, nr_subregions);
+
+	if (!last_nr_regions)
+		last_nr_regions = nr_regions;
 }
 
 /*

Signature · 1 line

2.17.1

SeongJae Park

author

2020-05-18 10:06 UTC #7 lore raw

PATCH v12 7/16 mm/damon: Apply dynamic memory mapping changes

In reply to SeongJae Park

From: SeongJae Park <[email protected]>

Only a number of parts in the virtual address space of the processes is mapped to physical memory and accessed. Thus, tracking the unmapped address regions is just wasteful. However, tracking every memory mapping change might incur an overhead. For the reason, DAMON applies the dynamic memory mapping changes to the tracking regions only for each of a user-specified time interval (``regions update interval``).

Signed-off-by SeongJae Park <[email protected]>

---
 include/linux/damon.h |  10 +++--
 mm/damon.c            | 101 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 106 insertions(+), 5 deletions(-)

include/linux/damon.h +7 -3

index f1c3f491fc50..62b9f90ed87b 100644
@@ -34,17 +34,21 @@ struct damon_task {
 /*
  * For each 'sample_interval', DAMON checks whether each region is accessed or
  * not.  It aggregates and keeps the access information (number of accesses to
- * each region) for each 'aggr_interval' time.
+ * each region) for 'aggr_interval' time.  DAMON also checks whether the memory
+ * mapping of the target tasks has changed (e.g., by mmap() calls from the
+ * application) and applies the changes for each 'regions_update_interval'.
  *
  * All time intervals are in micro-seconds.
  */
 struct damon_ctx {
 	unsigned long sample_interval;
 	unsigned long aggr_interval;
+	unsigned long regions_update_interval;
 	unsigned long min_nr_regions;
 	unsigned long max_nr_regions;
 
 	struct timespec64 last_aggregation;
+	struct timespec64 last_regions_update;
 
 	struct task_struct *kdamond;
 	bool kdamond_stop;

@@ -54,8 +58,8 @@ struct damon_ctx {
 };
 
 int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids);
-int damon_set_attrs(struct damon_ctx *ctx,
-		unsigned long sample_int, unsigned long aggr_int,
+int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
+		unsigned long aggr_int, unsigned long regions_update_int,
 		unsigned long min_nr_reg, unsigned long max_nr_reg);
 int damon_start(struct damon_ctx *ctx);
 int damon_stop(struct damon_ctx *ctx);

mm/damon.c +99 -2

131 lines not on this page · raw message

Signature · 1 line

2.17.1

SeongJae Park

author

2020-05-18 10:08 UTC #8 lore raw

PATCH v12 8/16 mm/damon: Implement callbacks

In reply to SeongJae Park

From: SeongJae Park <[email protected]>

This commit implements callbacks for DAMON. Using this, DAMON users can install their callbacks for each step of the access monitoring so that they can do something interesting with the monitored access patterns online. For example, callbacks can report the monitored patterns to users or do some access pattern based memory management such as proactive reclamations or access pattern based THP promotions/demotions decision makings.

Signed-off-by SeongJae Park <[email protected]>

---
 include/linux/damon.h | 4 ++++
 mm/damon.c            | 4 ++++
 2 files changed, 8 insertions(+)

include/linux/damon.h +4 -0

index 62b9f90ed87b..264569b21502 100644
@@ -55,6 +55,10 @@ struct damon_ctx {
 	struct mutex kdamond_lock;
 
 	struct list_head tasks_list;	/* 'damon_task' objects */
+
+	/* callbacks */
+	void (*sample_cb)(struct damon_ctx *context);
+	void (*aggregate_cb)(struct damon_ctx *context);
 };
 
 int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids);

mm/damon.c +4 -0

index 38a8a68b7beb..498160b5e086 100644
@@ -851,6 +851,8 @@ static int kdamond_fn(void *data)
 	kdamond_init_regions(ctx);
 	while (!kdamond_need_stop(ctx)) {
 		kdamond_prepare_access_checks(ctx);
+		if (ctx->sample_cb)
+			ctx->sample_cb(ctx);
 
 		usleep_range(ctx->sample_interval, ctx->sample_interval + 1);

@@ -858,6 +860,8 @@ static int kdamond_fn(void *data)
 
 		if (kdamond_aggregate_interval_passed(ctx)) {
 			kdamond_merge_regions(ctx, max_nr_accesses / 10);
+			if (ctx->aggregate_cb)
+				ctx->aggregate_cb(ctx);
 			kdamond_reset_aggregated(ctx);
 			kdamond_split_regions(ctx);
 		}

Signature · 1 line

2.17.1

SeongJae Park

author

2020-05-18 10:08 UTC #9 lore raw

PATCH v12 9/16 mm/damon: Implement access pattern recording

In reply to SeongJae Park

From: SeongJae Park <[email protected]>

This commit implements the recording feature of DAMON. If this feature is enabled, DAMON writes the monitored access patterns in its binary format into a file which specified by the user. This is already able to be implemented by each user using the callbacks. However, as the recording is expected to be used widely, this commit implements the feature in the DAMON, for more convenience and efficiency.

Signed-off-by SeongJae Park <[email protected]>

---
 include/linux/damon.h |   7 +++
 mm/damon.c            | 131 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 135 insertions(+), 3 deletions(-)

include/linux/damon.h +7 -0

index 264569b21502..bc46ea00e9a1 100644
@@ -50,6 +50,11 @@ struct damon_ctx {
 	struct timespec64 last_aggregation;
 	struct timespec64 last_regions_update;
 
+	unsigned char *rbuf;
+	unsigned int rbuf_len;
+	unsigned int rbuf_offset;
+	char *rfile_path;
+
 	struct task_struct *kdamond;
 	bool kdamond_stop;
 	struct mutex kdamond_lock;

@@ -65,6 +70,8 @@ int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids);
 int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
 		unsigned long aggr_int, unsigned long regions_update_int,
 		unsigned long min_nr_reg, unsigned long max_nr_reg);
+int damon_set_recording(struct damon_ctx *ctx,
+				unsigned int rbuf_len, char *rfile_path);
 int damon_start(struct damon_ctx *ctx);
 int damon_stop(struct damon_ctx *ctx);

mm/damon.c +128 -3

174 lines not on this page · raw message

Signature · 1 line

2.17.1

SeongJae Park

author

2020-05-18 10:09 UTC #10 lore raw

PATCH v12 10/16 mm/damon: Add debugfs interface

In reply to SeongJae Park

From: SeongJae Park <[email protected]>

This commit adds a debugfs interface for DAMON.

DAMON exports four files, ``attrs``, ``pids``, ``record``, and ``monitor_on`` under its debugfs directory, ``<debugfs>/damon/``.

Attributes
----------

Users can read and write the ``sampling interval``, ``aggregation interval``, ``regions update interval``, and min/max number of monitoring target regions by reading from and writing to the ``attrs`` file. For example, below commands set those values to 5 ms, 100 ms, 1,000 ms, 10, 1000 and check it again::

    # cd <debugfs>/damon
    # echo 5000 100000 1000000 10 1000 > attrs
    # cat attrs
    5000 100000 1000000 10 1000

Target PIDs
-----------

Users can read and write the pids of current monitoring target processes by reading from and writing to the ``pids`` file. For example, below commands set processes having pids 42 and 4242 as the processes to be monitored and check it again::

    # cd <debugfs>/damon
    # echo 42 4242 > pids
    # cat pids
    42 4242

Note that setting the pids doesn't start the monitoring.

Record
------

DAMON supports direct monitoring result record feature. The recorded results are first written to a buffer and flushed to a file in batch. Users can set the size of the buffer and the path to the result file by reading from and writing to the ``record`` file. For example, below commands set the buffer to be 4 KiB and the result to be saved in '/damon.data'.

    # cd <debugfs>/damon
    # echo 4096 /damon.data > pids
    # cat record
    4096 /damon.data

Turning On/Off
--------------

You can check current status, start and stop the monitoring by reading from and writing to the ``monitor_on`` file. Writing ``on`` to the file starts DAMON to monitor the target processes with the attributes. Writing ``off`` to the file stops DAMON. DAMON also stops if every target processes is terminated. Below example commands turn on, off, and check status of DAMON::

    # cd <debugfs>/damon
    # echo on > monitor_on
    # echo off > monitor_on
    # cat monitor_on
    off

Please note that you cannot write to the ``attrs`` and ``pids`` files while the monitoring is turned on. If you write to the files while DAMON is running, ``-EINVAL`` will be returned.

Signed-off-by SeongJae Park <[email protected]>

---
 mm/damon.c | 351 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 350 insertions(+), 1 deletion(-)

mm/damon.c +350 -1

index ddd78843f79a..f31310536c79 100644
@@ -10,6 +10,7 @@
 #define pr_fmt(fmt) "damon: " fmt
 
 #include <linux/damon.h>
+#include <linux/debugfs.h>
 #include <linux/delay.h>
 #include <linux/kthread.h>
 #include <linux/mm.h>

@@ -50,6 +51,15 @@
 /* Get a random number in [l, r) */
 #define damon_rand(l, r) (l + prandom_u32() % (r - l))
 
+/* A monitoring context for debugfs interface users. */
+static struct damon_ctx damon_user_ctx = {
+	.sample_interval = 5 * 1000,
+	.aggr_interval = 100 * 1000,
+	.regions_update_interval = 1000 * 1000,
+	.min_nr_regions = 10,
+	.max_nr_regions = 1000,
+};
+
 /*
  * Construct a damon_region struct
  *

@@ -1134,13 +1144,352 @@ int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
 	return 0;
 }
 
-static int __init damon_init(void)
+static ssize_t debugfs_monitor_on_read(struct file *file,
+		char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char monitor_on_buf[5];
+	bool monitor_on;
+	int len;
+
+	monitor_on = damon_kdamond_running(ctx);
+	len = snprintf(monitor_on_buf, 5, monitor_on ? "on\n" : "off\n");
+
+	return simple_read_from_buffer(buf, count, ppos, monitor_on_buf, len);
+}
+
+static ssize_t debugfs_monitor_on_write(struct file *file,
+		const char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	ssize_t ret;
+	char cmdbuf[5];
+	int err;
+
+	ret = simple_write_to_buffer(cmdbuf, 5, ppos, buf, count);
+	if (ret < 0)
+		return ret;
+
+	if (sscanf(cmdbuf, "%s", cmdbuf) != 1)
+		return -EINVAL;
+	if (!strncmp(cmdbuf, "on", 5))
+		err = damon_start(ctx);
+	else if (!strncmp(cmdbuf, "off", 5))
+		err = damon_stop(ctx);
+	else
+		return -EINVAL;
+
+	if (err)
+		ret = err;
+	return ret;
+}
+
+static ssize_t damon_sprint_pids(struct damon_ctx *ctx, char *buf, ssize_t len)
+{
+	struct damon_task *t;
+	int written = 0;
+	int rc;
+
+	damon_for_each_task(t, ctx) {
+		rc = snprintf(&buf[written], len - written, "%d ", t->pid);
+		if (!rc)
+			return -ENOMEM;
+		written += rc;
+	}
+	if (written)
+		written -= 1;
+	written += snprintf(&buf[written], len - written, "\n");
+	return written;
+}
+
+static ssize_t debugfs_pids_read(struct file *file,
+		char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	ssize_t len;
+	char pids_buf[320];
+
+	len = damon_sprint_pids(ctx, pids_buf, 320);
+	if (len < 0)
+		return len;
+
+	return simple_read_from_buffer(buf, count, ppos, pids_buf, len);
+}
+
+/*
+ * Converts a string into an array of unsigned long integers
+ *
+ * Returns an array of unsigned long integers if the conversion success, or
+ * NULL otherwise.
+ */
+static int *str_to_pids(const char *str, ssize_t len, ssize_t *nr_pids)
+{
+	int *pids;
+	const int max_nr_pids = 32;
+	int pid;
+	int pos = 0, parsed, ret;
+
+	*nr_pids = 0;
+	pids = kmalloc_array(max_nr_pids, sizeof(pid), GFP_KERNEL);
+	if (!pids)
+		return NULL;
+	while (*nr_pids < max_nr_pids && pos < len) {
+		ret = sscanf(&str[pos], "%d%n", &pid, &parsed);
+		pos += parsed;
+		if (ret != 1)
+			break;
+		pids[*nr_pids] = pid;
+		*nr_pids += 1;
+	}
+	if (*nr_pids == 0) {
+		kfree(pids);
+		pids = NULL;
+	}
+
+	return pids;
+}
+
+static ssize_t debugfs_pids_write(struct file *file,
+		const char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char *kbuf;
+	int *targets;
+	ssize_t nr_targets;
+	ssize_t ret;
+	int err;
+
+	kbuf = kmalloc(count, GFP_KERNEL);
+	if (!kbuf)
+		return -ENOMEM;
+
+	ret = simple_write_to_buffer(kbuf, count, ppos, buf, count);
+	if (ret < 0)
+		goto out;
+
+	targets = str_to_pids(kbuf, ret, &nr_targets);
+	if (!targets) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (ctx->kdamond) {
+		ret = -EINVAL;
+		goto unlock_out;
+	}
+
+	err = damon_set_pids(ctx, targets, nr_targets);
+	if (err)
+		ret = err;
+unlock_out:
+	mutex_unlock(&ctx->kdamond_lock);
+	kfree(targets);
+out:
+	kfree(kbuf);
+	return ret;
+}
+
+static ssize_t debugfs_record_read(struct file *file,
+		char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char record_buf[20 + MAX_RFILE_PATH_LEN];
+	int ret;
+
+	ret = snprintf(record_buf, ARRAY_SIZE(record_buf), "%u %s\n",
+			ctx->rbuf_len, ctx->rfile_path);
+	return simple_read_from_buffer(buf, count, ppos, record_buf, ret);
+}
+
+static ssize_t debugfs_record_write(struct file *file,
+		const char __user *buf, size_t count, loff_t *ppos)
 {
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char *kbuf;
+	unsigned int rbuf_len;
+	char rfile_path[MAX_RFILE_PATH_LEN];
+	ssize_t ret;
+	int err;
+
+	kbuf = kmalloc(count + 1, GFP_KERNEL);
+	if (!kbuf)
+		return -ENOMEM;
+	kbuf[count] = '\0';
+
+	ret = simple_write_to_buffer(kbuf, count, ppos, buf, count);
+	if (ret < 0)
+		goto out;
+	if (sscanf(kbuf, "%u %s",
+				&rbuf_len, rfile_path) != 2) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (ctx->kdamond) {
+		ret = -EBUSY;
+		goto unlock_out;
+	}
+
+	err = damon_set_recording(ctx, rbuf_len, rfile_path);
+	if (err)
+		ret = err;
+unlock_out:
+	mutex_unlock(&ctx->kdamond_lock);
+out:
+	kfree(kbuf);
+	return ret;
+}
+
+
+static ssize_t debugfs_attrs_read(struct file *file,
+		char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char kbuf[128];
+	int ret;
+
+	ret = snprintf(kbuf, ARRAY_SIZE(kbuf), "%lu %lu %lu %lu %lu\n",
+			ctx->sample_interval, ctx->aggr_interval,
+			ctx->regions_update_interval, ctx->min_nr_regions,
+			ctx->max_nr_regions);
+
+	return simple_read_from_buffer(buf, count, ppos, kbuf, ret);
+}
+
+static ssize_t debugfs_attrs_write(struct file *file,
+		const char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	unsigned long s, a, r, minr, maxr;
+	char *kbuf;
+	ssize_t ret;
+	int err;
+
+	kbuf = kmalloc(count, GFP_KERNEL);
+	if (!kbuf)
+		return -ENOMEM;
+
+	ret = simple_write_to_buffer(kbuf, count, ppos, buf, count);
+	if (ret < 0)
+		goto out;
+
+	if (sscanf(kbuf, "%lu %lu %lu %lu %lu",
+				&s, &a, &r, &minr, &maxr) != 5) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (ctx->kdamond) {
+		ret = -EBUSY;
+		goto unlock_out;
+	}
+
+	err = damon_set_attrs(ctx, s, a, r, minr, maxr);
+	if (err)
+		ret = err;
+unlock_out:
+	mutex_unlock(&ctx->kdamond_lock);
+out:
+	kfree(kbuf);
+	return ret;
+}
+
+static const struct file_operations monitor_on_fops = {
+	.owner = THIS_MODULE,
+	.read = debugfs_monitor_on_read,
+	.write = debugfs_monitor_on_write,
+};
+
+static const struct file_operations pids_fops = {
+	.owner = THIS_MODULE,
+	.read = debugfs_pids_read,
+	.write = debugfs_pids_write,
+};
+
+static const struct file_operations record_fops = {
+	.owner = THIS_MODULE,
+	.read = debugfs_record_read,
+	.write = debugfs_record_write,
+};
+
+static const struct file_operations attrs_fops = {
+	.owner = THIS_MODULE,
+	.read = debugfs_attrs_read,
+	.write = debugfs_attrs_write,
+};
+
+static struct dentry *debugfs_root;
+
+static int __init damon_debugfs_init(void)
+{
+	const char * const file_names[] = {"attrs", "record",
+		"pids", "monitor_on"};
+	const struct file_operations *fops[] = {&attrs_fops, &record_fops,
+		&pids_fops, &monitor_on_fops};
+	int i;
+
+	debugfs_root = debugfs_create_dir("damon", NULL);
+	if (!debugfs_root) {
+		pr_err("failed to create the debugfs dir\n");
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(file_names); i++) {
+		if (!debugfs_create_file(file_names[i], 0600, debugfs_root,
+					NULL, fops[i])) {
+			pr_err("failed to create %s file\n", file_names[i]);
+			return -ENOMEM;
+		}
+	}
+
 	return 0;
 }
 
+static int __init damon_init_user_ctx(void)
+{
+	int rc;
+
+	struct damon_ctx *ctx = &damon_user_ctx;
+
+	ktime_get_coarse_ts64(&ctx->last_aggregation);
+	ctx->last_regions_update = ctx->last_aggregation;
+
+	rc = damon_set_recording(ctx, 1024 * 1024, "/damon.data");
+	if (rc)
+		return rc;
+
+	mutex_init(&ctx->kdamond_lock);
+
+	INIT_LIST_HEAD(&ctx->tasks_list);
+
+	return 0;
+}
+
+static int __init damon_init(void)
+{
+	int rc;
+
+	rc = damon_init_user_ctx();
+	if (rc)
+		return rc;
+
+	rc = damon_debugfs_init();
+	if (rc)
+		pr_err("%s: debugfs init failed\n", __func__);
+
+	return rc;
+}
+
 static void __exit damon_exit(void)
 {
+	damon_stop(&damon_user_ctx);
+	debugfs_remove_recursive(debugfs_root);
+
+	kfree(damon_user_ctx.rbuf);
+	kfree(damon_user_ctx.rfile_path);
 }
 
 module_init(damon_init);

Signature · 1 line

2.17.1

SeongJae Park

author

2020-05-19 14:03 UTC #11 lore raw

Re: [PATCH v12 10/16] mm/damon: Add debugfs interface

Quoted 3 lines · On Mon, 18 May 2020 12:00:12 +0200 SeongJae Park <[email protected]> wrote:

From: SeongJae Park <[email protected]>
This commit adds a debugfs interface for DAMON.

[...]

Quoted 7 lines

mm/damon.c +0 -0

index ddd78843f79a..f31310536c79 100644
@@ -10,6 +10,7 @@
 #define pr_fmt(fmt) "damon: " fmt

[...]

Quoted 17 lines

mm/damon.c +17 -0

+
+static ssize_t damon_sprint_pids(struct damon_ctx *ctx, char *buf, ssize_t len)
+{
+	struct damon_task *t;
+	int written = 0;
+	int rc;
+
+	damon_for_each_task(t, ctx) {
+		rc = snprintf(&buf[written], len - written, "%d ", t->pid);
+		if (!rc)
+			return -ENOMEM;
+		written += rc;
+	}
+	if (written)
+		written -= 1;
+	written += snprintf(&buf[written], len - written, "\n");
+	return written;

mm/damon.c int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int, · line 1212

Quoted 10 lines

mm/damon.c +10 -0

+}
+
+static ssize_t debugfs_pids_read(struct file *file,
+		char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	ssize_t len;
+	char pids_buf[320];
+
+	len = damon_sprint_pids(ctx, pids_buf, 320);

This could race with concurrent pids debugfs file writers. Should be synchronized. Same to other debugfs files except 'monitor_on', which is already synchronized with corresponding writers.

I will enclose this function call with the context mutex in next revision.

Thanks,
SeongJae Park

Quoted 79 lines

mm/damon.c +79 -0

+	if (len < 0)
+		return len;
+
+	return simple_read_from_buffer(buf, count, ppos, pids_buf, len);
+}
+
+/*
+ * Converts a string into an array of unsigned long integers
+ *
+ * Returns an array of unsigned long integers if the conversion success, or
+ * NULL otherwise.
+ */
+static int *str_to_pids(const char *str, ssize_t len, ssize_t *nr_pids)
+{
+	int *pids;
+	const int max_nr_pids = 32;
+	int pid;
+	int pos = 0, parsed, ret;
+
+	*nr_pids = 0;
+	pids = kmalloc_array(max_nr_pids, sizeof(pid), GFP_KERNEL);
+	if (!pids)
+		return NULL;
+	while (*nr_pids < max_nr_pids && pos < len) {
+		ret = sscanf(&str[pos], "%d%n", &pid, &parsed);
+		pos += parsed;
+		if (ret != 1)
+			break;
+		pids[*nr_pids] = pid;
+		*nr_pids += 1;
+	}
+	if (*nr_pids == 0) {
+		kfree(pids);
+		pids = NULL;
+	}
+
+	return pids;
+}
+
+static ssize_t debugfs_pids_write(struct file *file,
+		const char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char *kbuf;
+	int *targets;
+	ssize_t nr_targets;
+	ssize_t ret;
+	int err;
+
+	kbuf = kmalloc(count, GFP_KERNEL);
+	if (!kbuf)
+		return -ENOMEM;
+
+	ret = simple_write_to_buffer(kbuf, count, ppos, buf, count);
+	if (ret < 0)
+		goto out;
+
+	targets = str_to_pids(kbuf, ret, &nr_targets);
+	if (!targets) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (ctx->kdamond) {
+		ret = -EINVAL;
+		goto unlock_out;
+	}
+
+	err = damon_set_pids(ctx, targets, nr_targets);
+	if (err)
+		ret = err;
+unlock_out:
+	mutex_unlock(&ctx->kdamond_lock);
+	kfree(targets);
+out:
+	kfree(kbuf);
+	return ret;
+}

[...]

SeongJae Park

author

2020-05-18 10:09 UTC #12 lore raw

PATCH v12 11/16 mm/damon: Add tracepoints

In reply to SeongJae Park

From: SeongJae Park <[email protected]>

This commit adds a tracepoint for DAMON. It traces the monitoring results of each region for each aggregation interval. Using this, DAMON will be easily integrated with any tracepoints supporting tools such as perf.

Signed-off-by SeongJae Park <[email protected]>

---
 include/trace/events/damon.h | 43 ++++++++++++++++++++++++++++++++++++
 mm/damon.c                   |  5 +++++
 2 files changed, 48 insertions(+)
 create mode 100644 include/trace/events/damon.h

include/trace/events/damon.h new file +43 -0

new file mode 100644
index 000000000000..22236642d366
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM damon
+
+#if !defined(_TRACE_DAMON_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_DAMON_H
+
+#include <linux/types.h>
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(damon_aggregated,
+
+	TP_PROTO(int pid, unsigned int nr_regions,
+		unsigned long vm_start, unsigned long vm_end,
+		unsigned int nr_accesses),
+
+	TP_ARGS(pid, nr_regions, vm_start, vm_end, nr_accesses),
+
+	TP_STRUCT__entry(
+		__field(int, pid)
+		__field(unsigned int, nr_regions)
+		__field(unsigned long, vm_start)
+		__field(unsigned long, vm_end)
+		__field(unsigned int, nr_accesses)
+	),
+
+	TP_fast_assign(
+		__entry->pid = pid;
+		__entry->nr_regions = nr_regions;
+		__entry->vm_start = vm_start;
+		__entry->vm_end = vm_end;
+		__entry->nr_accesses = nr_accesses;
+	),
+
+	TP_printk("pid=%d nr_regions=%u %lu-%lu: %u", __entry->pid,
+			__entry->nr_regions, __entry->vm_start,
+			__entry->vm_end, __entry->nr_accesses)
+);
+
+#endif /* _TRACE_DAMON_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>

mm/damon.c +5 -0

index f31310536c79..6fd55aec5275 100644
@@ -9,6 +9,8 @@
 
 #define pr_fmt(fmt) "damon: " fmt
 
+#define CREATE_TRACE_POINTS
+
 #include <linux/damon.h>
 #include <linux/debugfs.h>
 #include <linux/delay.h>

@@ -20,6 +22,7 @@
 #include <linux/sched/mm.h>
 #include <linux/sched/task.h>
 #include <linux/slab.h>
+#include <trace/events/damon.h>
 
 /* Minimal region size.  Every damon_region is aligned by this. */
 #define MIN_REGION PAGE_SIZE

@@ -650,6 +653,8 @@ static void kdamond_reset_aggregated(struct damon_ctx *c)
 			damon_write_rbuf(c, &r->vm_end, sizeof(r->vm_end));
 			damon_write_rbuf(c, &r->nr_accesses,
 					sizeof(r->nr_accesses));
+			trace_damon_aggregated(t->pid, nr,
+					r->vm_start, r->vm_end, r->nr_accesses);
 			r->nr_accesses = 0;
 		}
 	}

Signature · 1 line

2.17.1

SeongJae Park

author

2020-05-18 10:10 UTC #13 lore raw

PATCH v12 12/16 tools: Add a minimal user-space tool for DAMON

In reply to SeongJae Park

From: SeongJae Park <[email protected]>

This commit adds a shallow wrapper python script, ``/tools/damon/damo`` that provides more convenient interface. Note that it is only aimed to be used for minimal reference of the DAMON's debugfs interfaces and for debugging of the DAMON itself.

Signed-off-by SeongJae Park <[email protected]>

---
 tools/damon/.gitignore    |   1 +
 tools/damon/_dist.py      |  36 ++++
 tools/damon/_recfile.py   |  23 +++
 tools/damon/bin2txt.py    |  67 +++++++
 tools/damon/damo          |  37 ++++
 tools/damon/heats.py      | 362 ++++++++++++++++++++++++++++++++++++++
 tools/damon/nr_regions.py |  91 ++++++++++
 tools/damon/record.py     | 212 ++++++++++++++++++++++
 tools/damon/report.py     |  45 +++++
 tools/damon/wss.py        |  97 ++++++++++
 10 files changed, 971 insertions(+)
 create mode 100644 tools/damon/.gitignore
 create mode 100644 tools/damon/_dist.py
 create mode 100644 tools/damon/_recfile.py
 create mode 100644 tools/damon/bin2txt.py
 create mode 100755 tools/damon/damo
 create mode 100644 tools/damon/heats.py
 create mode 100644 tools/damon/nr_regions.py
 create mode 100644 tools/damon/record.py
 create mode 100644 tools/damon/report.py
 create mode 100644 tools/damon/wss.py

tools/damon/.gitignore new file +1 -0

new file mode 100644
index 000000000000..96403d36ff93
@@ -0,0 +1 @@
+__pycache__/*

tools/damon/_dist.py new file +36 -0

new file mode 100644
index 000000000000..9851ec964e5c
@@ -0,0 +1,36 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import os
+import struct
+import subprocess
+
+def access_patterns(f):
+    nr_regions = struct.unpack('I', f.read(4))[0]
+
+    patterns = []
+    for r in range(nr_regions):
+        saddr = struct.unpack('L', f.read(8))[0]
+        eaddr = struct.unpack('L', f.read(8))[0]
+        nr_accesses = struct.unpack('I', f.read(4))[0]
+        patterns.append([eaddr - saddr, nr_accesses])
+    return patterns
+
+def plot_dist(data_file, output_file, xlabel, ylabel):
+    terminal = output_file.split('.')[-1]
+    if not terminal in ['pdf', 'jpeg', 'png', 'svg']:
+        os.remove(data_file)
+        print("Unsupported plot output type.")
+        exit(-1)
+
+    gnuplot_cmd = """
+    set term %s;
+    set output '%s';
+    set key off;
+    set xlabel '%s';
+    set ylabel '%s';
+    plot '%s' with linespoints;""" % (terminal, output_file, xlabel, ylabel,
+            data_file)
+    subprocess.call(['gnuplot', '-e', gnuplot_cmd])
+    os.remove(data_file)
+

tools/damon/_recfile.py new file +23 -0

new file mode 100644
index 000000000000..331b4d8165d8
@@ -0,0 +1,23 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import struct
+
+fmt_version = 0
+
+def set_fmt_version(f):
+    global fmt_version
+
+    mark = f.read(16)
+    if mark == b'damon_recfmt_ver':
+        fmt_version = struct.unpack('i', f.read(4))[0]
+    else:
+        fmt_version = 0
+        f.seek(0)
+    return fmt_version
+
+def pid(f):
+    if fmt_version == 0:
+        return struct.unpack('L', f.read(8))[0]
+    else:
+        return struct.unpack('i', f.read(4))[0]

tools/damon/bin2txt.py new file +67 -0

67 lines not on this page · raw message

tools/damon/damo new file +37 -0

new file mode 100755
index 000000000000..58e1099ae5fc
@@ -0,0 +1,37 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import argparse
+
+import record
+import report
+
+class SubCmdHelpFormatter(argparse.RawDescriptionHelpFormatter):
+    def _format_action(self, action):
+        parts = super(argparse.RawDescriptionHelpFormatter,
+                self)._format_action(action)
+        # skip sub parsers help
+        if action.nargs == argparse.PARSER:
+            parts = '\n'.join(parts.split('\n')[1:])
+        return parts
+
+parser = argparse.ArgumentParser(formatter_class=SubCmdHelpFormatter)
+
+subparser = parser.add_subparsers(title='command', dest='command',
+        metavar='<command>')
+subparser.required = True
+
+parser_record = subparser.add_parser('record',
+        help='record data accesses of the given target processes')
+record.set_argparser(parser_record)
+
+parser_report = subparser.add_parser('report',
+        help='report the recorded data accesses in the specified form')
+report.set_argparser(parser_report)
+
+args = parser.parse_args()
+
+if args.command == 'record':
+    record.main(args)
+elif args.command == 'report':
+    report.main(args)

tools/damon/heats.py new file +362 -0

362 lines not on this page · raw message

tools/damon/nr_regions.py new file +91 -0

91 lines not on this page · raw message

tools/damon/record.py new file +212 -0

212 lines not on this page · raw message

tools/damon/report.py new file +45 -0

45 lines not on this page · raw message

tools/damon/wss.py new file +97 -0

97 lines not on this page · raw message

Signature · 1 line

2.17.1

SeongJae Park

author

2020-05-18 10:11 UTC #14 lore raw

PATCH v12 13/16 Documentation/admin-guide/mm: Add a document for DAMON

In reply to SeongJae Park

From: SeongJae Park <[email protected]>

This commit adds a simple document for DAMON under Documentation/admin-guide/mm.

Signed-off-by SeongJae Park <[email protected]>

---
 Documentation/admin-guide/mm/damon/api.rst    |   9 +
 .../admin-guide/mm/damon/damon_heatmap.png    | Bin 0 -> 8366 bytes
 .../admin-guide/mm/damon/damon_wss_change.png | Bin 0 -> 7211 bytes
 .../admin-guide/mm/damon/damon_wss_dist.png   | Bin 0 -> 6173 bytes
 Documentation/admin-guide/mm/damon/faq.rst    |  39 +++
 .../admin-guide/mm/damon/freqmine_heatmap.png | Bin 0 -> 8687 bytes
 .../admin-guide/mm/damon/freqmine_wss_sz.png  | Bin 0 -> 4986 bytes
 .../mm/damon/freqmine_wss_time.png            | Bin 0 -> 6283 bytes
 Documentation/admin-guide/mm/damon/guide.rst  | 196 +++++++++++
 Documentation/admin-guide/mm/damon/index.rst  |  50 +++
 .../admin-guide/mm/damon/mechanisms.rst       | 111 +++++++
 Documentation/admin-guide/mm/damon/plans.rst  |  49 +++
 Documentation/admin-guide/mm/damon/start.rst  | 119 +++++++
 .../mm/damon/streamcluster_heatmap.png        | Bin 0 -> 37916 bytes
 .../mm/damon/streamcluster_wss_sz.png         | Bin 0 -> 5522 bytes
 .../mm/damon/streamcluster_wss_time.png       | Bin 0 -> 6322 bytes
 Documentation/admin-guide/mm/damon/usage.rst  | 305 ++++++++++++++++++
 Documentation/admin-guide/mm/index.rst        |   1 +
 Documentation/index.rst                       | 176 +---------
 19 files changed, 887 insertions(+), 168 deletions(-)
 create mode 100644 Documentation/admin-guide/mm/damon/api.rst
 create mode 100644 Documentation/admin-guide/mm/damon/damon_heatmap.png
 create mode 100644 Documentation/admin-guide/mm/damon/damon_wss_change.png
 create mode 100644 Documentation/admin-guide/mm/damon/damon_wss_dist.png
 create mode 100644 Documentation/admin-guide/mm/damon/faq.rst
 create mode 100644 Documentation/admin-guide/mm/damon/freqmine_heatmap.png
 create mode 100644 Documentation/admin-guide/mm/damon/freqmine_wss_sz.png
 create mode 100644 Documentation/admin-guide/mm/damon/freqmine_wss_time.png
 create mode 100644 Documentation/admin-guide/mm/damon/guide.rst
 create mode 100644 Documentation/admin-guide/mm/damon/index.rst
 create mode 100644 Documentation/admin-guide/mm/damon/mechanisms.rst
 create mode 100644 Documentation/admin-guide/mm/damon/plans.rst
 create mode 100644 Documentation/admin-guide/mm/damon/start.rst
 create mode 100644 Documentation/admin-guide/mm/damon/streamcluster_heatmap.png
 create mode 100644 Documentation/admin-guide/mm/damon/streamcluster_wss_sz.png
 create mode 100644 Documentation/admin-guide/mm/damon/streamcluster_wss_time.png
 create mode 100644 Documentation/admin-guide/mm/damon/usage.rst

Documentation/admin-guide/mm/damon/api.rst new file +9 -0

new file mode 100644
index 000000000000..2249d2116b39
@@ -0,0 +1,9 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=============
+API Reference
+=============
+
+.. kernel-doc:: include/linux/damon.h
+
+.. kernel-doc:: mm/damon.c

Documentation/admin-guide/mm/damon/damon_heatmap.png new file binary +0 -0

new file mode 100644
index 0000000000000000000000000000000000000000..ff485f9f59ca2717f5221b2824eaaed616b22c0e
GIT binary patch

Documentation/admin-guide/mm/damon/damon_wss_change.png new file binary +0 -0

new file mode 100644
index 0000000000000000000000000000000000000000..36699547c342cd05c9f416c78bc3fc86b9dc415e
GIT binary patch

Documentation/admin-guide/mm/damon/damon_wss_dist.png new file binary +0 -0

new file mode 100644
index 0000000000000000000000000000000000000000..3c390f5115af9bcf7bd76ccdf9414de8ace9799b
GIT binary patch

Documentation/admin-guide/mm/damon/faq.rst new file +39 -0

new file mode 100644
index 000000000000..7ea52d1078a0
@@ -0,0 +1,39 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==========================
+Frequently Asked Questions
+==========================
+
+Why a new module, instead of extending perf or other user space tools?
+======================================================================
+
+First, because it needs to be lightweight as much as possible so that it can be
+used online, any unnecessary overhead such as kernel - user space context
+switching cost should be avoided.  Second, DAMON aims to be used by other
+programs including the kernel.  Therefore, having a dependency on specific
+tools like perf is not desirable.  These are the two biggest reasons why DAMON
+is implemented in the kernel space.
+
+
+Can 'idle pages tracking' or 'perf mem' substitute DAMON?
+=========================================================
+
+Idle page tracking is a low level primitive for access check of each physical
+page frame.  'perf mem' is similar, though it can use sampling to minimize the
+overhead.  DAMON is a higher-level framework for access patterns of data objects
+that focused on memory management optimization and providing sophisticated
+features for that including the overhead handling.  Therefore, 'idle pages
+tracking' and 'perf mem' could provide a subset of DAMON's output, but cannot
+substitute DAMON.  Rather than that, DAMON could use those as it's low-level
+primitives.
+
+
+Does DAMON support virtual memory only?
+========================================
+
+For now, yes.  But, DAMON will be able to support various address spaces
+including physical memory in near future.  An RFC patchset [1]_ for this
+extension is already available.  Please refer :doc:`plans` for detailed plan
+for this.
+
+.. [1] https://lore.kernel.org/linux-mm/[email protected]/

Documentation/admin-guide/mm/damon/freqmine_heatmap.png new file binary +0 -0

new file mode 100644
index 0000000000000000000000000000000000000000..9641bade4e2e52cfaf77ac2ef50607239ab90899
GIT binary patch

Documentation/admin-guide/mm/damon/freqmine_wss_sz.png new file binary +0 -0

new file mode 100644
index 0000000000000000000000000000000000000000..28049dec5fabfca0ca33896ee6b667dc116aacbf
GIT binary patch

Documentation/admin-guide/mm/damon/freqmine_wss_time.png new file binary +0 -0

new file mode 100644
index 0000000000000000000000000000000000000000..3ca9df7ee11a9cf650fc75497f653345eba28eea
GIT binary patch

Documentation/admin-guide/mm/damon/guide.rst new file +196 -0

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Documentation/admin-guide/mm/damon/index.rst new file +50 -0

50 lines not on this page · raw message

Documentation/admin-guide/mm/damon/mechanisms.rst new file +111 -0

111 lines not on this page · raw message

Documentation/admin-guide/mm/damon/plans.rst new file +49 -0

49 lines not on this page · raw message

Documentation/admin-guide/mm/damon/start.rst new file +119 -0

119 lines not on this page · raw message

Documentation/admin-guide/mm/damon/streamcluster_heatmap.png new file binary +0 -0

new file mode 100644
index 0000000000000000000000000000000000000000..c9186f63bca4292a3f2e7602b2095c46914b9ae0
GIT binary patch

Documentation/admin-guide/mm/damon/streamcluster_wss_sz.png new file binary +0 -0

new file mode 100644
index 0000000000000000000000000000000000000000..8ea84a454233d3ab5f754d8cbdef78a15b134f70
GIT binary patch

Documentation/admin-guide/mm/damon/streamcluster_wss_time.png new file binary +0 -0

new file mode 100644
index 0000000000000000000000000000000000000000..b4f19cce225e43e7b0c23563245c19ebe5ed3f0c
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Documentation/admin-guide/mm/damon/usage.rst new file +305 -0

305 lines not on this page · raw message

Documentation/admin-guide/mm/index.rst +1 -0

index 11db46448354..d3d0ba373eb6 100644
@@ -27,6 +27,7 @@ the Linux memory management.
 
    concepts
    cma_debugfs
+   data_access_monitor
    hugetlbpage
    idle_page_tracking
    ksm

Documentation/index.rst +8 ~~-168~~

191 lines not on this page · raw message

Signature · 1 line

2.17.1

SeongJae Park

author

2020-05-18 10:13 UTC #15 lore raw

PATCH v12 14/16 mm/damon: Add kunit tests

In reply to SeongJae Park

From: SeongJae Park <[email protected]>

This commit adds kunit based unit tests for DAMON.

Signed-off-by SeongJae Park <[email protected]>

Reviewed-by Brendan Higgins <[email protected]>

---
 mm/Kconfig      |  11 +
 mm/damon-test.h | 622 ++++++++++++++++++++++++++++++++++++++++++++++++
 mm/damon.c      |   6 +
 3 files changed, 639 insertions(+)
 create mode 100644 mm/damon-test.h

mm/Kconfig +11 -0

index 9ea49633a6df..81ace52f1c23 100644
@@ -751,4 +751,15 @@ config DAMON
 	  and 2) sufficiently light-weight so that it can be applied online.
 	  If unsure, say N.
 
+config DAMON_KUNIT_TEST
+	bool "Test for damon"
+	depends on DAMON=y && KUNIT
+	help
+	  This builds the DAMON Kunit test suite.
+
+	  For more information on KUnit and unit tests in general, please refer
+	  to the KUnit documentation.
+
+	  If unsure, say N.
+
 endmenu

mm/damon-test.h new file +622 -0

622 lines not on this page · raw message

mm/damon.c +6 -0

index 6fd55aec5275..fa8be37a8bbd 100644
@@ -25,7 +25,11 @@
 #include <trace/events/damon.h>
 
 /* Minimal region size.  Every damon_region is aligned by this. */
+#ifndef CONFIG_DAMON_KUNIT_TEST
 #define MIN_REGION PAGE_SIZE
+#else
+#define MIN_REGION 1
+#endif
 
 #define damon_get_task_struct(t) \
 	(get_pid_task(find_vpid(t->pid), PIDTYPE_PID))

@@ -1503,3 +1507,5 @@ module_exit(damon_exit);
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("SeongJae Park <[email protected]>");
 MODULE_DESCRIPTION("DAMON: Data Access MONitor");
+
+#include "damon-test.h"

Signature · 1 line

2.17.1

SeongJae Park

author

2020-05-18 10:13 UTC #16 lore raw

PATCH v12 15/16 mm/damon: Add user space selftests

In reply to SeongJae Park

From: SeongJae Park <[email protected]>

This commit adds a simple user space tests for DAMON. The tests are using kselftest framework.

Signed-off-by SeongJae Park <[email protected]>

---
 tools/testing/selftests/damon/Makefile        |   7 +
 .../selftests/damon/_chk_dependency.sh        |  28 ++++
 tools/testing/selftests/damon/_chk_record.py  | 108 ++++++++++++++
 .../testing/selftests/damon/debugfs_attrs.sh  | 139 ++++++++++++++++++
 .../testing/selftests/damon/debugfs_record.sh |  50 +++++++
 5 files changed, 332 insertions(+)
 create mode 100644 tools/testing/selftests/damon/Makefile
 create mode 100644 tools/testing/selftests/damon/_chk_dependency.sh
 create mode 100644 tools/testing/selftests/damon/_chk_record.py
 create mode 100755 tools/testing/selftests/damon/debugfs_attrs.sh
 create mode 100755 tools/testing/selftests/damon/debugfs_record.sh

tools/testing/selftests/damon/Makefile new file +7 -0

new file mode 100644
index 000000000000..cfd5393a4639
@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0
+# Makefile for damon selftests
+
+TEST_FILES = _chk_dependency.sh _chk_record_file.py
+TEST_PROGS = debugfs_attrs.sh debugfs_record.sh
+
+include ../lib.mk

tools/testing/selftests/damon/_chk_dependency.sh new file +28 -0

new file mode 100644
index 000000000000..814dcadd5e96
@@ -0,0 +1,28 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
+DBGFS=/sys/kernel/debug/damon
+
+if [ $EUID -ne 0 ];
+then
+	echo "Run as root"
+	exit $ksft_skip
+fi
+
+if [ ! -d $DBGFS ]
+then
+	echo "$DBGFS not found"
+	exit $ksft_skip
+fi
+
+for f in attrs record pids monitor_on
+do
+	if [ ! -f "$DBGFS/$f" ]
+	then
+		echo "$f not found"
+		exit 1
+	fi
+done

tools/testing/selftests/damon/_chk_record.py new file +108 -0

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tools/testing/selftests/damon/debugfs_attrs.sh new file +139 -0

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tools/testing/selftests/damon/debugfs_record.sh new file +50 -0

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Signature · 1 line

2.17.1

SeongJae Park

author

2020-05-18 10:14 UTC #17 lore raw

PATCH v12 16/16 MAINTAINERS: Update for DAMON

In reply to SeongJae Park

From: SeongJae Park <[email protected]>

This commit updates MAINTAINERS file for DAMON related files.

Signed-off-by SeongJae Park <[email protected]>

---
 MAINTAINERS | 12 ++++++++++++
 1 file changed, 12 insertions(+)

MAINTAINERS +12 -0

index 5a5332b3591d..586513e92b65 100644
@@ -4661,6 +4661,18 @@ F:	net/ax25/ax25_out.c
 F:	net/ax25/ax25_timer.c
 F:	net/ax25/sysctl_net_ax25.c
 
+DATA ACCESS MONITOR
+M:	SeongJae Park <[email protected]>
+L:	[email protected]
+S:	Maintained
+F:	Documentation/admin-guide/mm/damon/*
+F:	include/linux/damon.h
+F:	include/trace/events/damon.h
+F:	mm/damon-test.h
+F:	mm/damon.c
+F:	tools/damon/*
+F:	tools/testing/selftests/damon/*
+
 DAVICOM FAST ETHERNET (DMFE) NETWORK DRIVER
 L:	[email protected]
 S:	Orphan

Signature · 1 line

2.17.1