Hackbench pipes regression bisected to PSI
Mel Gorman
Acked-by Tejun Heo Acked-by Peter Zijlstra (Intel) Tested-by Daniel Drake Tested-by Suren BaghdasaryanHi Johannes,
PSI is a great idea but it does have overhead and if enabled by Kconfig then it incurs a hit whether the user is aware of the feature or not. I think enabling by default is unnecessary as it should only be enabled if the information is being consumed. While the Kconfig exists, it's all or nothing if distributions want to have the feature available.
I've included a bisection report below showing a 6-10% regression on a single socket skylake machine. Would you mind doing one or all of the following to fix it please?
a) disable it by default
b) put psi_disable behind a static branch to move the overhead to zero if it's disabled
c) optionally enable/disable at runtime (least important as at a glance, this may be problematic)
Thanks
Bisect parameters
=================CONFIG_AUTO=openSUSE-LEAP-15.0
BUILD_TYPE=make
MACHINE=delboy
BISECT_REVERSE=no
BISECT_MMTESTS_TEST=hackbench-process-pipes
BISECT_CONFIG=global-dhp__scheduler-unbound
BISECT_GOOD=v4.19
BISECT_BAD=92b419289cee
BISECT_LOGDIR=/srv/marvin/impera/bisections-sigma-delboy-global-dhp__scheduler-unbound-openSUSE-LEAP-15.0-openSUSE-LEAP-15.0-v4.19..92b419289cee
BISECT_COMPARE=Amean
BISECT_PREFER=Lower
BISECT_CLIENT="5"
BISECT_REBOOT_CLEAN=no
BISECT_MONITOR_CONFIG=
BISECT_NO_MITIGATIONS=no
BISECT_COMMAND="bisection-run --machine delboy --distro openSUSE-LEAP-15.0 --kernel-config openSUSE-LEAP-15.0 --tree make --config global-dhp__scheduler-unbound --mmtests-test hackbench-process-pipes --monitor no-monitor --method sigma --good v4.19 --bad 92b419289cee --walk-mainline --notify [email protected] --bisect-client 5 --mmtests-limit --iterations 1 --logdir /srv/marvin/impera/bisections-sigma-delboy-global-dhp__scheduler-unbound-openSUSE-LEAP-15.0-openSUSE-LEAP-15.0-v4.19..92b419289cee --reset-trees" BISECT_LOGDIR=/srv/marvin/impera/bisections-sigma-delboy-global-dhp__scheduler-unbound-openSUSE-LEAP-15.0-openSUSE-LEAP-15.0-v4.19..92b419289cee
Last good/First bad commit
==========================
Last good commit: eb414681d5a07d28d2ff90dc05f69ec6b232ebd2 First bad commit: 2ce7135adc9ad081aa3c49744144376ac74fea60
Quoted 1 line
From
2ce7135adc9ad081aa3c49744144376ac74fea60Mon Sep 17 00:00:00 2001
From: Johannes Weiner <[email protected]>
Date: Fri, 26 Oct 2018 15:06:31 -0700
Subject: [PATCH] psi: cgroup support
On a system that executes multiple cgrouped jobs and independent workloads, we don't just care about the health of the overall system, but also that of individual jobs, so that we can ensure individual job health, fairness between jobs, or prioritize some jobs over others. This patch implements pressure stall tracking for cgroups. In kernels with CONFIG_PSI=y, cgroup2 groups will have cpu.pressure, memory.pressure, and io.pressure files that track aggregate pressure stall times for only the tasks inside the cgroup.
Documentation/accounting/psi.txt | 9 +++ Documentation/admin-guide/cgroup-v2.rst | 18 +++++ include/linux/cgroup-defs.h | 4 ++ include/linux/cgroup.h | 15 ++++ include/linux/psi.h | 25 +++++++ init/Kconfig | 4 ++ kernel/cgroup/cgroup.c | 45 +++++++++++- kernel/sched/psi.c | 118 +++++++++++++++++++++++++++++--- 8 files changed, 228 insertions(+), 10 deletions(-)
Comparison
==========
initial initial last penup first
good-v4.19 bad-92b419289cee good-eb414681 good-95f9ab2d bad-2ce7135a
Min 1 1.2980 ( 0.00%) 1.2950 ( 0.23%) 1.2870 ( 0.85%) 1.3100 ( -0.92%) 1.3190 ( -1.62%) Min 3 3.8480 ( 0.00%) 4.0640 ( -5.61%) 3.8070 ( 1.07%) 3.8530 ( -0.13%) 4.1750 ( -8.50%) Min 5 6.7420 ( 0.00%) 8.1480 ( -20.85%) 6.8010 ( -0.88%) 6.7740 ( -0.47%) 7.3370 ( -8.83%) Min 7 9.7230 ( 0.00%) 10.2490 ( -5.41%) 9.7840 ( -0.63%) 9.8940 ( -1.76%) 10.6890 ( -9.94%) Min 12 16.2810 ( 0.00%) 17.6470 ( -8.39%) 16.1740 ( 0.66%) 16.2390 ( 0.26%) 17.1260 ( -5.19%) Min 18 25.2050 ( 0.00%) 25.6510 ( -1.77%) 25.4950 ( -1.15%) 25.4130 ( -0.83%) 25.5330 ( -1.30%) Min 24 31.7720 ( 0.00%) 29.4380 ( 7.35%) 33.3800 ( -5.06%) 31.2400 ( 1.67%) 31.4640 ( 0.97%) Min 30 37.0100 ( 0.00%) 37.6760 ( -1.80%) 33.7630 ( 8.77%) 37.5890 ( -1.56%) 33.2980 ( 10.03%) Min 32 40.0150 ( 0.00%) 39.9460 ( 0.17%) 37.5790 ( 6.09%) 37.7580 ( 5.64%) 38.8230 ( 2.98%) Amean 1 1.3153 ( 0.00%) 1.3530 ( -2.86%) 1.3133 ( 0.15%) 1.3217 ( -0.48%) 1.3243 ( -0.68%) Amean 3 3.8670 ( 0.00%) 4.1097 * -6.28%* 3.8597 ( 0.19%) 3.8943 ( -0.71%) 4.2130 * -8.95%* Amean 5 6.8563 ( 0.00%) 8.3113 * -21.22%* 6.9197 ( -0.92%) 6.8630 ( -0.10%) 7.5630 * -10.31%* Amean 7 9.8650 ( 0.00%) 10.5607 * -7.05%* 9.9627 ( -0.99%) 9.9177 ( -0.53%) 10.7880 * -9.36%* Amean 12 16.5540 ( 0.00%) 18.2850 * -10.46%* 16.7513 ( -1.19%) 16.3700 ( 1.11%) 18.1283 * -9.51%* Amean 18 26.0390 ( 0.00%) 27.4333 ( -5.35%) 27.0223 ( -3.78%) 25.8067 ( 0.89%) 27.2333 ( -4.59%) Amean 24 32.8650 ( 0.00%) 33.0093 ( -0.44%) 34.6167 ( -5.33%) 32.7020 ( 0.50%) 34.9150 ( -6.24%) Amean 30 39.5653 ( 0.00%) 41.0643 ( -3.79%) 36.6733 ( 7.31%) 39.4050 ( 0.41%) 38.1273 ( 3.63%) Amean 32 40.8177 ( 0.00%) 42.1383 ( -3.24%) 39.1487 ( 4.09%) 41.7743 ( -2.34%) 39.4193 * 3.43%* Stddev 1 0.0158 ( 0.00%) 0.0730 (-361.51%) 0.0247 ( -56.14%) 0.0102 ( 35.44%) 0.0061 ( 61.38%) Stddev 3 0.0271 ( 0.00%) 0.0397 ( -46.65%) 0.0627 (-131.53%) 0.0575 (-112.38%) 0.0330 ( -22.06%) Stddev 5 0.1491 ( 0.00%) 0.1744 ( -16.95%) 0.1134 ( 23.94%) 0.0771 ( 48.30%) 0.2126 ( -42.57%) Stddev 7 0.1650 ( 0.00%) 0.2780 ( -68.48%) 0.1663 ( -0.80%) 0.0257 ( 84.43%) 0.0889 ( 46.12%) Stddev 12 0.2395 ( 0.00%) 0.5652 (-135.95%) 0.5726 (-139.03%) 0.1626 ( 32.11%) 0.8698 (-263.10%) Stddev 18 0.8499 ( 0.00%) 1.5949 ( -87.65%) 1.3650 ( -60.60%) 0.3799 ( 55.31%) 1.5393 ( -81.11%) Stddev 24 1.2105 ( 0.00%) 3.3274 (-174.88%) 1.5403 ( -27.25%) 1.2683 ( -4.78%) 3.1545 (-160.60%) Stddev 30 2.4625 ( 0.00%) 2.9472 ( -19.69%) 2.5228 ( -2.45%) 1.5773 ( 35.95%) 5.3969 (-119.17%) Stddev 32 0.9572 ( 0.00%) 2.4088 (-151.66%) 1.5982 ( -66.97%) 4.3986 (-359.54%) 0.5216 ( 45.50%) CoeffVar 1 1.2029 ( 0.00%) 5.3969 (-348.67%) 1.8811 ( -56.38%) 0.7728 ( 35.75%) 0.4614 ( 61.64%) CoeffVar 3 0.7001 ( 0.00%) 0.9661 ( -37.99%) 1.6241 (-131.97%) 1.4765 (-110.89%) 0.7844 ( -12.03%) CoeffVar 5 2.1749 ( 0.00%) 2.0982 ( 3.53%) 1.6392 ( 24.63%) 1.1233 ( 48.35%) 2.8110 ( -29.25%) CoeffVar 7 1.6725 ( 0.00%) 2.6322 ( -57.38%) 1.6694 ( 0.18%) 0.2591 ( 84.51%) 0.8241 ( 50.73%) CoeffVar 12 1.4470 ( 0.00%) 3.0910 (-113.61%) 3.4180 (-136.21%) 0.9934 ( 31.35%) 4.7978 (-231.56%) CoeffVar 18 3.2640 ( 0.00%) 5.8138 ( -78.12%) 5.0512 ( -54.75%) 1.4719 ( 54.91%) 5.6523 ( -73.17%) CoeffVar 24 3.6832 ( 0.00%) 10.0801 (-173.68%) 4.4495 ( -20.81%) 3.8785 ( -5.30%) 9.0349 (-145.30%) CoeffVar 30 6.2238 ( 0.00%) 7.1770 ( -15.32%) 6.8792 ( -10.53%) 4.0027 ( 35.69%) 14.1550 (-127.43%) CoeffVar 32 2.3450 ( 0.00%) 5.7165 (-143.78%) 4.0825 ( -74.09%) 10.5295 (-349.02%) 1.3233 ( 43.57%) Max 1 1.3290 ( 0.00%) 1.4350 ( -7.98%) 1.3360 ( -0.53%) 1.3290 ( 0.00%) 1.3310 ( -0.15%) Max 3 3.8980 ( 0.00%) 4.1360 ( -6.11%) 3.9290 ( -0.80%) 3.9600 ( -1.59%) 4.2350 ( -8.65%) Max 5 7.0250 ( 0.00%) 8.4950 ( -20.93%) 7.0270 ( -0.03%) 6.9090 ( 1.65%) 7.7590 ( -10.45%) Max 7 10.0460 ( 0.00%) 10.7830 ( -7.34%) 10.1130 ( -0.67%) 9.9450 ( 1.01%) 10.8610 ( -8.11%) Max 12 16.7290 ( 0.00%) 18.7230 ( -11.92%) 17.3190 ( -3.53%) 16.5520 ( 1.06%) 18.6840 ( -11.69%) Max 18 26.9040 ( 0.00%) 28.7260 ( -6.77%) 28.1230 ( -4.53%) 26.1710 ( 2.72%) 28.5320 ( -6.05%) Max 24 34.1660 ( 0.00%) 36.0220 ( -5.43%) 36.3420 ( -6.37%) 33.5080 ( 1.93%) 37.6500 ( -10.20%) Max 30 41.9230 ( 0.00%) 43.0330 ( -2.65%) 38.2390 ( 8.79%) 40.4330 ( 3.55%) 43.9530 ( -4.84%) Max 32 41.8770 ( 0.00%) 44.7170 ( -6.78%) 40.7740 ( 2.63%) 46.4750 ( -10.98%) 39.7910 ( 4.98%) BAmean-50 1 1.3085 ( 0.00%) 1.3120 ( -0.27%) 1.3020 ( 0.50%) 1.3180 ( -0.73%) 1.3210 ( -0.96%) BAmean-50 3 3.8515 ( 0.00%) 4.0965 ( -6.36%) 3.8250 ( 0.69%) 3.8615 ( -0.26%) 4.2020 ( -9.10%) BAmean-50 5 6.7720 ( 0.00%) 8.2195 ( -21.37%) 6.8660 ( -1.39%) 6.8400 ( -1.00%) 7.4650 ( -10.23%) BAmean-50 7 9.7745 ( 0.00%) 10.4495 ( -6.91%) 9.8875 ( -1.16%) 9.9040 ( -1.32%) 10.7515 ( -10.00%) BAmean-50 12 16.4665 ( 0.00%) 18.0660 ( -9.71%) 16.4675 ( -0.01%) 16.2790 ( 1.14%) 17.8505 ( -8.40%) BAmean-50 18 25.6065 ( 0.00%) 26.7870 ( -4.61%) 26.4720 ( -3.38%) 25.6245 ( -0.07%) 26.5840 ( -3.82%) BAmean-50 24 32.2145 ( 0.00%) 31.5030 ( 2.21%) 33.7540 ( -4.78%) 32.2990 ( -0.26%) 33.5475 ( -4.14%) BAmean-50 30 38.3865 ( 0.00%) 40.0800 ( -4.41%) 35.8905 ( 6.50%) 38.8910 ( -1.31%) 35.2145 ( 8.26%) BAmean-50 32 40.2880 ( 0.00%) 40.8490 ( -1.39%) 38.3360 ( 4.85%) 39.4240 ( 2.14%) 39.2335 ( 2.62%) BAmean-95 1 1.3153 ( 0.00%) 1.3530 ( -2.86%) 1.3133 ( 0.15%) 1.3217 ( -0.48%) 1.3243 ( -0.68%) BAmean-95 3 3.8670 ( 0.00%) 4.1097 ( -6.28%) 3.8597 ( 0.19%) 3.8943 ( -0.71%) 4.2130 ( -8.95%) BAmean-95 5 6.8563 ( 0.00%) 8.3113 ( -21.22%) 6.9197 ( -0.92%) 6.8630 ( -0.10%) 7.5630 ( -10.31%) BAmean-95 7 9.8650 ( 0.00%) 10.5607 ( -7.05%) 9.9627 ( -0.99%) 9.9177 ( -0.53%) 10.7880 ( -9.36%) BAmean-95 12 16.5540 ( 0.00%) 18.2850 ( -10.46%) 16.7513 ( -1.19%) 16.3700 ( 1.11%) 18.1283 ( -9.51%) BAmean-95 18 26.0390 ( 0.00%) 27.4333 ( -5.35%) 27.0223 ( -3.78%) 25.8067 ( 0.89%) 27.2333 ( -4.59%) BAmean-95 24 32.8650 ( 0.00%) 33.0093 ( -0.44%) 34.6167 ( -5.33%) 32.7020 ( 0.50%) 34.9150 ( -6.24%) BAmean-95 30 39.5653 ( 0.00%) 41.0643 ( -3.79%) 36.6733 ( 7.31%) 39.4050 ( 0.41%) 38.1273 ( 3.63%) BAmean-95 32 40.8177 ( 0.00%) 42.1383 ( -3.24%) 39.1487 ( 4.09%) 41.7743 ( -2.34%) 39.4193 ( 3.43%) BAmean-99 1 1.3153 ( 0.00%) 1.3530 ( -2.86%) 1.3133 ( 0.15%) 1.3217 ( -0.48%) 1.3243 ( -0.68%) BAmean-99 3 3.8670 ( 0.00%) 4.1097 ( -6.28%) 3.8597 ( 0.19%) 3.8943 ( -0.71%) 4.2130 ( -8.95%) BAmean-99 5 6.8563 ( 0.00%) 8.3113 ( -21.22%) 6.9197 ( -0.92%) 6.8630 ( -0.10%) 7.5630 ( -10.31%) BAmean-99 7 9.8650 ( 0.00%) 10.5607 ( -7.05%) 9.9627 ( -0.99%) 9.9177 ( -0.53%) 10.7880 ( -9.36%) BAmean-99 12 16.5540 ( 0.00%) 18.2850 ( -10.46%) 16.7513 ( -1.19%) 16.3700 ( 1.11%) 18.1283 ( -9.51%) BAmean-99 18 26.0390 ( 0.00%) 27.4333 ( -5.35%) 27.0223 ( -3.78%) 25.8067 ( 0.89%) 27.2333 ( -4.59%) BAmean-99 24 32.8650 ( 0.00%) 33.0093 ( -0.44%) 34.6167 ( -5.33%) 32.7020 ( 0.50%) 34.9150 ( -6.24%) BAmean-99 30 39.5653 ( 0.00%) 41.0643 ( -3.79%) 36.6733 ( 7.31%) 39.4050 ( 0.41%) 38.1273 ( 3.63%) BAmean-99 32 40.8177 ( 0.00%) 42.1383 ( -3.24%) 39.1487 ( 4.09%) 41.7743 ( -2.34%) 39.4193 ( 3.43%)
Git log
=======
git bisect start
# good: [84df9525b0c27f3ebc2ebb1864fa62a97fdedb7d] Linux 4.19
git bisect good 84df9525b0c27f3ebc2ebb1864fa62a97fdedb7d
# bad: [92b419289ceecdd1eae03114928913f298b84327] Merge tag 'riscv-for-linus-4.20-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/palmer/riscv-linux
git bisect bad 92b419289ceecdd1eae03114928913f298b84327
# good: [84df9525b0c27f3ebc2ebb1864fa62a97fdedb7d] Linux 4.19
git bisect good 84df9525b0c27f3ebc2ebb1864fa62a97fdedb7d
# good: [26873acacbdbb4e4b444f5dd28dcc4853f0e8ba2] Merge tag 'driver-core-4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core
git bisect good 26873acacbdbb4e4b444f5dd28dcc4853f0e8ba2
# bad: [738b04fba18d35cd352b7b15afefb8a7b798648e] Merge tag 'staging-4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging
git bisect bad 738b04fba18d35cd352b7b15afefb8a7b798648e
# good: [f2bfc71aee75feff33ca659322b72ffeed5a243d] Merge tag 'drm-intel-next-fixes-2018-10-18' of git://anongit.freedesktop.org/drm/drm-intel into drm-next git bisect good f2bfc71aee75feff33ca659322b72ffeed5a243d
# bad: [345671ea0f9258f410eb057b9ced9cefbbe5dc78] Merge branch 'akpm' (patches from Andrew)
git bisect bad 345671ea0f9258f410eb057b9ced9cefbbe5dc78
# good: [033078a9afe504ac9e615d10c4b35d634450b637] Merge tag '4.20-smb3-fixes' of git://git.samba.org/sfrench/cifs-2.6
git bisect good 033078a9afe504ac9e615d10c4b35d634450b637
# good: [685f7e4f161425b137056abe35ba8ef7b669d83d] Merge tag 'powerpc-4.20-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux
git bisect good 685f7e4f161425b137056abe35ba8ef7b669d83d
# bad: [d3035be4ce2345d98633a45f93a74e526e94b802] mm: calculate deferred pages after skipping mirrored memory
git bisect bad d3035be4ce2345d98633a45f93a74e526e94b802
# good: [95f9ab2d596e8cbb388315e78c82b9a131bf2928] mm: workingset: don't drop refault information prematurely
git bisect good 95f9ab2d596e8cbb388315e78c82b9a131bf2928
# bad: [f682a97a00591def7cefbb5003dc04045028e405] mm: provide kernel parameter to allow disabling page init poisoning
git bisect bad f682a97a00591def7cefbb5003dc04045028e405
# bad: [c3df29d13044d885695067fa0b1386824942557a] mm/swap.c: remove duplicated include
git bisect bad c3df29d13044d885695067fa0b1386824942557a
# good: [eb414681d5a07d28d2ff90dc05f69ec6b232ebd2] psi: pressure stall information for CPU, memory, and IO
git bisect good eb414681d5a07d28d2ff90dc05f69ec6b232ebd2
# bad: [68d48e6a2df575b935edd420396c3cb8b6aa6ad3] mm: workingset: add vmstat counter for shadow nodes
git bisect bad 68d48e6a2df575b935edd420396c3cb8b6aa6ad3
# bad: [505802a53510e54ad5fbbd655a68893df83bfb91] mm: workingset: use cheaper __inc_lruvec_state in irqsafe node reclaim
git bisect bad 505802a53510e54ad5fbbd655a68893df83bfb91
# bad: [2ce7135adc9ad081aa3c49744144376ac74fea60] psi: cgroup support
git bisect bad 2ce7135adc9ad081aa3c49744144376ac74fea60
# first bad commit: [2ce7135adc9ad081aa3c49744144376ac74fea60] psi: cgroup support
Signature · 2 lines
Mel Gorman SUSE Labs
Johannes Weiner
maintainerHi Mel,
Quoted 7 lines · Mel Gorman
Hi Johannes,
PSI is a great idea but it does have overhead and if enabled by
Kconfigthen it incurs a hit whether the user is aware of the feature or not. I think enabling by default is unnecessary as it should only be enabled if the information is being consumed. While theKconfigexists, it's all or nothing if distributions want to have the feature available.
Yes, let's make this easier to pick and choose. Obviously I'd rather you shipped it default-disabled than not at all.
Quoted 9 lines
I've included a bisection report below showing a 6-10% regression on a single socket skylake machine. Would you mind doing one or all of the following to fix it please?
a) disable it by default
b) putpsi_disablebehind a static branch to move the overhead to zero if it's disabled
c) optionally enable/disable at runtime (least important as at a glance, this may be problematic)
For a) I'd suggest we do what we do in other places that face this vendor kernel trade-off (NUMA balancing comes to mind): one option to build the feature, one option to set whether the default is on or off.
And b) is pretty straight-forward, let's do that too.
c) is not possible, as we need the complete task counts to calculate pressure, and maintaining those counts are where the sched cost is.
Quoted 8 lines
Last good/First bad commit
==========================
Last good commit:eb414681d5a07d28d2ff90dc05f69ec6b232ebd2First bad commit:2ce7135adc9ad081aa3c49744144376ac74fea60From2ce7135adc9ad081aa3c49744144376ac74fea60Mon Sep 17 00:00:00 2001
From: Johannes Weiner <[email protected]>
Date: Fri, 26 Oct 2018 15:06:31 -0700
Subject: [PATCH] psi: cgroup support
Quoted 8 lines
On a system that executes multiple cgrouped jobs and independent workloads, we don't just care about the health of the overall system, but also that of individual jobs, so that we can ensure individual job health, fairness between jobs, or prioritize some jobs over others. This patch implements pressure stall tracking for cgroups. In kernels with
CONFIG_PSI=y, cgroup2 groups will have cpu.pressure, memory.pressure, and io.pressure files that track aggregate pressure stall times for only the tasks inside the cgroup.
It's curious that the cgroup support patch is the offender, not the psi patch itself (that adds some cost as per the hackbench results, but not as much). What kind of cgroup setup does this code run in?
Anyway, how about the following?
From 6ae33455b8083fc9f5d5fbfe971f70253b0dbacd Mon Sep 17 00:00:00 2001
From: Johannes Weiner <[email protected]>
Date: Mon, 26 Nov 2018 09:39:23 -0500
Subject: [PATCH] psi: make disabling/enabling easier for vendor kernels
Mel Gorman reports a hackbench regression with psi that would prohibit shipping the suse kernel with it default-enabled, but he'd still like users to be able to opt in at little to no cost to others.
With the current combination of CONFIG_PSI and the psi_disabled bool set from the commandline, this is a challenge. Do the following things to make it easier:
1. Add a config option CONFIG_PSI_DEFAULT_ENABLED that allows distros to enable CONFIG_PSI in their kernel, but leaving the feature disabled unless a user requests it at boot-time.
To avoid double negatives, rename psi_disabled= to psi_enable=.
2. Make psi_disabled a static branch to eliminate any branch costs when the feature is disabled.
--- include/linux/psi.h | 3 ++- init/Kconfig | 9 +++++++++ kernel/sched/psi.c | 30 +++++++++++++++++++++--------- kernel/sched/stats.h | 8 ++++---- 4 files changed, 36 insertions(+), 14 deletions(-)
include/linux/psi.h +2 -1
@@ -1,6 +1,7 @@#ifndef _LINUX_PSI_H#define _LINUX_PSI_H +#include <linux/jump_label.h> #include <linux/psi_types.h> #include <linux/sched.h>
@@ -9,7 +10,7 @@ struct css_set;#ifdef CONFIG_PSI -extern bool psi_disabled; +extern struct static_key_false psi_disabled;void psi_init (void );
init/Kconfig +9 -0
@@ -509,6 +509,15 @@ config PSI Say N if unsure. +config PSI_DEFAULT_DISABLED + bool "Require boot parameter to enable pressure stall information tracking" + default n + depends on PSI + help + If set, pressure stall information tracking will be disabled + per default but can be enabled through passing psi_enable=1 + on the kernel commandline during boot. + endmenu # "CPU/Task time and stats accounting" config CPU_ISOLATION
kernel/sched/psi.c +21 -9
@@ -136,8 +136,18 @@static int psi_bug__read_mostly ; -bool psi_disabled__read_mostly ; -core_param (psi_disabled, psi_disabled, bool,0644 ); +DEFINE_STATIC_KEY_FALSE (psi_disabled); + +#ifdef CONFIG_PSI_DEFAULT_DISABLED +bool psi_enable; +#else +bool psi_enable = true; +#endif +static int __init parse_psi_enable (char *str) +{ +return kstrtobool (str, &psi_enable) ==0 ; +} +__setup ("psi_enable=" , parse_psi_enable);/* Running averages - we need to be higher-res than loadavg */ #define PSI_FREQ (2*HZ+1)/* 2 sec intervals */
@@ -169,8 +179,10 @@ static void group_init(struct psi_group *group)void __init psi_init (void ) { -if (psi_disabled) +if (!psi_enable) { +static_branch_enable (&psi_disabled);return ; + } psi_period =jiffies_to_nsecs (PSI_FREQ );group_init (&psi_system);
@@ -549,7 +561,7 @@ void psi_memstall_enter(unsigned long *flags)struct rq_flags rf;struct rq *rq; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ; *flags = current->flags &PF_MEMSTALL ;
@@ -579,7 +591,7 @@ void psi_memstall_leave(unsigned long *flags)struct rq_flags rf;struct rq *rq; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;if (*flags)
@@ -600,7 +612,7 @@ void psi_memstall_leave(unsigned long *flags)#ifdef CONFIG_CGROUPS int psi_cgroup_alloc (struct cgroup *cgroup) { -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return 0 ; cgroup->psi.pcpu = alloc_percpu(struct psi_group_cpu);
@@ -612,7 +624,7 @@ int psi_cgroup_alloc(struct cgroup *cgroup)void psi_cgroup_free (struct cgroup *cgroup) { -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;cancel_delayed_work_sync (&cgroup->psi.clock_work);
@@ -637,7 +649,7 @@ void cgroup_move_task(struct task_struct *task, struct css_set *to)struct rq_flags rf;struct rq *rq; -if (psi_disabled) { +if (static_branch_likely (&psi_disabled)) {/* * Lame to do this here, but the scheduler cannot be locked * from the outside, so we move cgroups from inside sched/.
@@ -673,7 +685,7 @@ int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res) {int full; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return -EOPNOTSUPP ;update_stats (group);
kernel/sched/stats.h +4 -4
@@ -66,7 +66,7 @@ static inline void psi_enqueue(struct task_struct *p, bool wakeup) {int clear =0 , set =TSK_RUNNING ; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;if (!wakeup || p->sched_psi_wake_requeue) {
@@ -86,7 +86,7 @@ static inline void psi_dequeue(struct task_struct *p, bool sleep) {int clear =TSK_RUNNING , set =0 ; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;if (!sleep) {
@@ -102,7 +102,7 @@ static inline void psi_dequeue(struct task_struct *p, bool sleep)static inline void psi_ttwu_dequeue (struct task_struct *p) { -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;/* * Is the task being migrated during a wakeup? Make sure to
@@ -128,7 +128,7 @@ static inline void psi_ttwu_dequeue(struct task_struct *p)static inline void psi_task_tick (struct rq *rq) { -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;if (unlikely (rq->curr->flags &PF_MEMSTALL ))
Signature · 1 line
2.19.1
Quoted 5 lines · Johannes Weiner
Hi Mel,
Quoted 2 lines · Mel Gorman
Hi Johannes,
Quoted 9 lines
Quoted 5 lines
PSI is a great idea but it does have overhead and if enabled by
Kconfigthen it incurs a hit whether the user is aware of the feature or not. I think enabling by default is unnecessary as it should only be enabled if the information is being consumed. While theKconfigexists, it's all or nothing if distributions want to have the feature available.Yes, let's make this easier to pick and choose. Obviously I'd rather you shipped it default-disabled than not at all.
Indeed.
Quoted 10 lines
Quoted 9 lines
I've included a bisection report below showing a 6-10% regression on a single socket skylake machine. Would you mind doing one or all of the following to fix it please?
a) disable it by default
b) putpsi_disablebehind a static branch to move the overhead to zero if it's disabled
c) optionally enable/disable at runtime (least important as at a glance, this may be problematic)
Quoted 4 lines
For a) I'd suggest we do what we do in other places that face this vendor kernel trade-off (NUMA balancing comes to mind): one option to build the feature, one option to set whether the default is on or off.
That would be fine and makes sense.
Quoted 2 lines
And b) is pretty straight-forward, let's do that too.
Thanks.
Quoted 3 lines
c) is not possible, as we need the complete task counts to calculate pressure, and maintaining those counts are where the sched cost is.
I figured that this would be the case.
Quoted 17 lines
Quoted 8 lines
Last good/First bad commit
==========================
Last good commit:eb414681d5a07d28d2ff90dc05f69ec6b232ebd2First bad commit:2ce7135adc9ad081aa3c49744144376ac74fea60From2ce7135adc9ad081aa3c49744144376ac74fea60Mon Sep 17 00:00:00 2001
From: Johannes Weiner <[email protected]>
Date: Fri, 26 Oct 2018 15:06:31 -0700
Subject: [PATCH] psi: cgroup supportQuoted 8 lines
On a system that executes multiple cgrouped jobs and independent workloads, we don't just care about the health of the overall system, but also that of individual jobs, so that we can ensure individual job health, fairness between jobs, or prioritize some jobs over others. This patch implements pressure stall tracking for cgroups. In kernels with
CONFIG_PSI=y, cgroup2 groups will have cpu.pressure, memory.pressure, and io.pressure files that track aggregate pressure stall times for only the tasks inside the cgroup.
Quoted 4 lines
It's curious that the cgroup support patch is the offender, not the psi patch itself (that adds some cost as per the hackbench results, but not as much). What kind of cgroup setup does this code run in?
No cgroup is setup but given that it is an automatic bisection, it's not very unusual for it to get "close" but not get it exactly right.
Quoted 2 lines
Anyway, how about the following?
I've queued it up setting CONFIG_PSI_DEFAULT_DISABLED in the Kconfig.
Quoted 11 lines
<SNIP>
init/Kconfig +1
-0@@ -509,6 +509,15 @@ config PSI Say N if unsure. +config PSI_DEFAULT_DISABLED
init/Kconfig config PSI · line 522
Quoted 10 lines
init/Kconfig +8
-0+ bool "Require boot parameter to enable pressure stall information tracking" + default n + depends on PSI + help + If set, pressure stall information tracking will be disabled + per default but can be enabled through passing psi_enable=1 + on the kernel commandline during boot. + endmenu # "CPU/Task time and stats accounting"
Should this default y on the basis that someone only wants the feature if they are aware of it? This is not that important as CONFIG_PSI is disabled by default and it's up to distribution maintainers to use their brain.
Quoted 14 lines
init/Kconfig +0
-0config CPU_ISOLATIONkernel/sched/psi.c +3
-2@@ -136,8 +136,18 @@static int psi_bug__read_mostly ; -bool psi_disabled__read_mostly ; -core_param (psi_disabled, psi_disabled, bool,0644 ); +DEFINE_STATIC_KEY_FALSE (psi_disabled); + +#ifdef CONFIG_PSI_DEFAULT_DISABLED
kernel/sched/psi.c line 151
Quoted 10 lines
kernel/sched/psi.c +9
-0+bool psi_enable; +#else +bool psi_enable = true; +#endif +static int __init parse_psi_enable (char *str) +{ +return kstrtobool (str, &psi_enable) ==0 ; +} +__setup ("psi_enable=" , parse_psi_enable);
Bit late to notice but this switch should be in Documentation/admin-guide/kernel-parameters.txt. If you really want to match the automatic numa balancing switch then it also should be psi=[enable|disable] instead of psi_enable=[1|0]
Signature · 2 lines
Mel Gorman SUSE Labs
Johannes Weiner
maintainerQuoted 5 lines · Mel Gorman
Quoted 4 lines · Johannes Weiner
(quoted diff) +0
-0@@ -509,6 +509,15 @@ config PSI Say N if unsure.
Quoted 15 lines
Review config PSI · line 522
Quoted 11 lines
(quoted diff) +9
-0+config PSI_DEFAULT_DISABLED + bool "Require boot parameter to enable pressure stall information tracking" + default n + depends on PSI + help + If set, pressure stall information tracking will be disabled + per default but can be enabled through passing psi_enable=1 + on the kernel commandline during boot. + endmenu # "CPU/Task time and stats accounting"Should this default y on the basis that someone only wants the feature if they are aware of it? This is not that important as
CONFIG_PSIis disabled by default and it's up to distribution maintainers to use their brain.
I went with the NUMA balancing example again here, which defaults to enabling the feature at boot time. IMO that makes sense, as somebody would presumably first read through the PSI help text, then decide y on that before being asked the second question. A "yes, but <stipulations>" for vendor kernels seems more appropriate than requiring a double yes for other users to simply get the feature.
Quoted 16 lines
Quoted 16 lines
(quoted diff) +10
-2@@ -136,8 +136,18 @@ static int psi_bug __read_mostly; -bool psi_disabled __read_mostly; -core_param(psi_disabled, psi_disabled, bool, 0644); +DEFINE_STATIC_KEY_FALSE(psi_disabled); + +#ifdef CONFIG_PSI_DEFAULT_DISABLED +bool psi_enable; +#else +bool psi_enable = true; +#endif +static int __init parse_psi_enable(char *str) +{ + return kstrtobool(str, &psi_enable) == 0;
Quoted 8 lines
Review line 151
Quoted 3 lines
(quoted diff) +2
-0+} +__setup("psi_enable=", parse_psi_enable);Bit late to notice but this switch should be in
Documentation/admin-guide/kernel-parameters.txt. If you really want to match the automatic numa balancing switch then it also should be psi=[enable|disable] instead of psi_enable=[1|0]
Done and done, thanks. Updated patch:
---
Quoted 1 line
From
694ae3d82da06ca57bfaa775140941ac5e8f2e37Mon Sep 17 00:00:00 2001
From: Johannes Weiner <[email protected]>
Date: Mon, 26 Nov 2018 09:39:23 -0500
Subject: [PATCH] psi: make disabling/enabling easier for vendor kernels
Mel Gorman reports a hackbench regression with psi that would prohibit shipping the suse kernel with it default-enabled, but he'd still like users to be able to opt in at little to no cost to others.
With the current combination of CONFIG_PSI and the psi_disabled bool set from the commandline, this is a challenge. Do the following things to make it easier:
1. Add a config option CONFIG_PSI_DEFAULT_ENABLED that allows distros to enable CONFIG_PSI in their kernel, but leaving the feature disabled unless a user requests it at boot-time.
To avoid double negatives, rename psi_disabled= to psi=.
2. Make psi_disabled a static branch to eliminate any branch costs when the feature is disabled.
--- .../admin-guide/kernel-parameters.txt | 4 +++ include/linux/psi.h | 3 +- init/Kconfig | 9 ++++++ kernel/sched/psi.c | 30 +++++++++++++------ kernel/sched/stats.h | 8 ++--- 5 files changed, 40 insertions(+), 14 deletions(-)
Documentation/admin-guide/kernel-parameters.txt +4 -0
@@ -3504,6 +3504,10 @@ before loading. See Documentation/blockdev/ramdisk.txt. + psi= [KNL] Enable or disable pressure stall information + tracking. + Format: <bool> + psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to probe for; one of (bare|imps|exps|lifebook|any). psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
include/linux/psi.h +2 -1
@@ -1,6 +1,7 @@#ifndef _LINUX_PSI_H#define _LINUX_PSI_H +#include <linux/jump_label.h> #include <linux/psi_types.h> #include <linux/sched.h>
@@ -9,7 +10,7 @@ struct css_set;#ifdef CONFIG_PSI -extern bool psi_disabled; +extern struct static_key_false psi_disabled;void psi_init (void );
init/Kconfig +9 -0
@@ -509,6 +509,15 @@ config PSI Say N if unsure. +config PSI_DEFAULT_DISABLED + bool "Require boot parameter to enable pressure stall information tracking" + default n + depends on PSI + help + If set, pressure stall information tracking will be disabled + per default but can be enabled through passing psi_enable=1 + on the kernel commandline during boot. + endmenu # "CPU/Task time and stats accounting" config CPU_ISOLATION
kernel/sched/psi.c +21 -9
@@ -136,8 +136,18 @@static int psi_bug__read_mostly ; -bool psi_disabled__read_mostly ; -core_param (psi_disabled, psi_disabled, bool,0644 ); +DEFINE_STATIC_KEY_FALSE (psi_disabled); + +#ifdef CONFIG_PSI_DEFAULT_DISABLED +bool psi_enable; +#else +bool psi_enable = true; +#endif +static int __init setup_psi (char *str) +{ +return kstrtobool (str, &psi_enable) ==0 ; +} +__setup ("psi=" , setup_psi);/* Running averages - we need to be higher-res than loadavg */ #define PSI_FREQ (2*HZ+1)/* 2 sec intervals */
@@ -169,8 +179,10 @@ static void group_init(struct psi_group *group)void __init psi_init (void ) { -if (psi_disabled) +if (!psi_enable) { +static_branch_enable (&psi_disabled);return ; + } psi_period =jiffies_to_nsecs (PSI_FREQ );group_init (&psi_system);
@@ -549,7 +561,7 @@ void psi_memstall_enter(unsigned long *flags)struct rq_flags rf;struct rq *rq; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ; *flags = current->flags &PF_MEMSTALL ;
@@ -579,7 +591,7 @@ void psi_memstall_leave(unsigned long *flags)struct rq_flags rf;struct rq *rq; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;if (*flags)
@@ -600,7 +612,7 @@ void psi_memstall_leave(unsigned long *flags)#ifdef CONFIG_CGROUPS int psi_cgroup_alloc (struct cgroup *cgroup) { -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return 0 ; cgroup->psi.pcpu = alloc_percpu(struct psi_group_cpu);
@@ -612,7 +624,7 @@ int psi_cgroup_alloc(struct cgroup *cgroup)void psi_cgroup_free (struct cgroup *cgroup) { -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;cancel_delayed_work_sync (&cgroup->psi.clock_work);
@@ -637,7 +649,7 @@ void cgroup_move_task(struct task_struct *task, struct css_set *to)struct rq_flags rf;struct rq *rq; -if (psi_disabled) { +if (static_branch_likely (&psi_disabled)) {/* * Lame to do this here, but the scheduler cannot be locked * from the outside, so we move cgroups from inside sched/.
@@ -673,7 +685,7 @@ int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res) {int full; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return -EOPNOTSUPP ;update_stats (group);
kernel/sched/stats.h +4 -4
@@ -66,7 +66,7 @@ static inline void psi_enqueue(struct task_struct *p, bool wakeup) {int clear =0 , set =TSK_RUNNING ; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;if (!wakeup || p->sched_psi_wake_requeue) {
@@ -86,7 +86,7 @@ static inline void psi_dequeue(struct task_struct *p, bool sleep) {int clear =TSK_RUNNING , set =0 ; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;if (!sleep) {
@@ -102,7 +102,7 @@ static inline void psi_dequeue(struct task_struct *p, bool sleep)static inline void psi_ttwu_dequeue (struct task_struct *p) { -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;/* * Is the task being migrated during a wakeup? Make sure to
@@ -128,7 +128,7 @@ static inline void psi_ttwu_dequeue(struct task_struct *p)static inline void psi_task_tick (struct rq *rq) { -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;if (unlikely (rq->curr->flags &PF_MEMSTALL ))
Signature · 1 line
2.19.1
Quoted 22 lines · Johannes Weiner
Quoted 5 lines · Mel Gorman
Quoted 4 lines · Johannes Weiner
init/Kconfig +0
-0@@ -509,6 +509,15 @@ config PSI Say N if unsure.Quoted 15 lines
init/Kconfig config PSI · line 522
Quoted 11 lines
init/Kconfig +9
-0+config PSI_DEFAULT_DISABLED + bool "Require boot parameter to enable pressure stall information tracking" + default n + depends on PSI + help + If set, pressure stall information tracking will be disabled + per default but can be enabled through passing psi_enable=1 + on the kernel commandline during boot. + endmenu # "CPU/Task time and stats accounting"Should this default y on the basis that someone only wants the feature if they are aware of it? This is not that important as
CONFIG_PSIis disabled by default and it's up to distribution maintainers to use their brain.
Quoted 7 lines
I went with the NUMA balancing example again here, which defaults to enabling the feature at boot time. IMO that makes sense, as somebody would presumably first read through the PSI help text, then decide y on that before being asked the second question. A "yes, but <stipulations>" for vendor kernels seems more appropriate than requiring a double yes for other users to simply get the feature.
That's fair enough. The original NUMA balancing thinking was that it should be enabled because there is a reasonable expectation that it would improve performance regardless of user awareness. PSI is not necessarily the same as it requires a consumer but I accept that a distro maintainer should read the Kconfig text and figure it out.
I'll make sure the updated version gets tested, thanks.
Signature · 2 lines
Mel Gorman SUSE Labs
Mel Gorman
Tested-byQuoted 8 lines · Johannes Weiner
Quoted 5 lines
Bit late to notice but this switch should be in
Documentation/admin-guide/kernel-parameters.txt. If you really want to match the automatic numa balancing switch then it also should be psi=[enable|disable] instead of psi_enable=[1|0]Done and done, thanks. Updated patch:
The following is a comparision using CONFIG_PSI=n as a baseline against your patch and a vanilla kernel
4.20.0-rc4 4.20.0-rc4 4.20.0-rc4
kconfigdisable-v1r1 vanilla psidisable-v1r1
Amean 1 1.3100 ( 0.00%) 1.3923 ( -6.28%) 1.3427 ( -2.49%) Amean 3 3.8860 ( 0.00%) 4.1230 * -6.10%* 3.8860 ( -0.00%) Amean 5 6.8847 ( 0.00%) 8.0390 * -16.77%* 6.7727 ( 1.63%) Amean 7 9.9310 ( 0.00%) 10.8367 * -9.12%* 9.9910 ( -0.60%) Amean 12 16.6577 ( 0.00%) 18.2363 * -9.48%* 17.1083 ( -2.71%) Amean 18 26.5133 ( 0.00%) 27.8833 * -5.17%* 25.7663 ( 2.82%) Amean 24 34.3003 ( 0.00%) 34.6830 ( -1.12%) 32.0450 ( 6.58%) Amean 30 40.0063 ( 0.00%) 40.5800 ( -1.43%) 41.5087 ( -3.76%) Amean 32 40.1407 ( 0.00%) 41.2273 ( -2.71%) 39.9417 ( 0.50%)
It's showing that the vanilla kernel takes a hit (as the bisection indicated it would) and that disabling PSI by default is reasonably close in terms of performance for this particular workload on this particular machine so;
Thanks!
Signature · 2 lines
Mel Gorman SUSE Labs
Quoted 15 lines · Mel Gorman
The following is a comparision using
CONFIG_PSI=nas a baseline against your patch and a vanilla kernel4.20.0-rc4 4.20.0-rc4 4.20.0-rc4
kconfigdisable-v1r1 vanilla psidisable-v1r1Amean 1 1.3100 ( 0.00%) 1.3923 ( -6.28%) 1.3427 ( -2.49%) Amean 3 3.8860 ( 0.00%) 4.1230 * -6.10%* 3.8860 ( -0.00%) Amean 5 6.8847 ( 0.00%) 8.0390 * -16.77%* 6.7727 ( 1.63%) Amean 7 9.9310 ( 0.00%) 10.8367 * -9.12%* 9.9910 ( -0.60%) Amean 12 16.6577 ( 0.00%) 18.2363 * -9.48%* 17.1083 ( -2.71%) Amean 18 26.5133 ( 0.00%) 27.8833 * -5.17%* 25.7663 ( 2.82%) Amean 24 34.3003 ( 0.00%) 34.6830 ( -1.12%) 32.0450 ( 6.58%) Amean 30 40.0063 ( 0.00%) 40.5800 ( -1.43%) 41.5087 ( -3.76%) Amean 32 40.1407 ( 0.00%) 41.2273 ( -2.71%) 39.9417 ( 0.50%)
Quoted 6 lines
It's showing that the vanilla kernel takes a hit (as the bisection indicated it would) and that disabling PSI by default is reasonably close in terms of performance for this particular workload on this particular machine so;
Tested-by Mel Gorman <[email protected]>
Thanks for testing it. Let's add these results to the changelog:
---
Quoted 1 line
From
347b69a52d1ec7e71df1108cbc5703d6dd0616baMon Sep 17 00:00:00 2001
From: Johannes Weiner <[email protected]>
Date: Mon, 26 Nov 2018 09:39:23 -0500
Subject: [PATCH] psi: make disabling/enabling easier for vendor kernels
Mel Gorman reports a hackbench regression with psi that would prohibit shipping the suse kernel with it default-enabled, but he'd still like users to be able to opt in at little to no cost to others.
With the current combination of CONFIG_PSI and the psi_disabled bool set from the commandline, this is a challenge. Do the following things to make it easier:
1. Add a config option CONFIG_PSI_DEFAULT_ENABLED that allows distros to enable CONFIG_PSI in their kernel, but leaving the feature disabled unless a user requests it at boot-time.
To avoid double negatives, rename psi_disabled= to psi=.
2. Make psi_disabled a static branch to eliminate any branch costs when the feature is disabled.
In terms of numbers before and after this patch, Mel says:
: The following is a comparision using CONFIG_PSI=n as a baseline against : your patch and a vanilla kernel
:
: 4.20.0-rc4 4.20.0-rc4 4.20.0-rc4
: kconfigdisable-v1r1 vanilla psidisable-v1r1 : Amean 1 1.3100 ( 0.00%) 1.3923 ( -6.28%) 1.3427 ( -2.49%) : Amean 3 3.8860 ( 0.00%) 4.1230 * -6.10%* 3.8860 ( -0.00%) : Amean 5 6.8847 ( 0.00%) 8.0390 * -16.77%* 6.7727 ( 1.63%) : Amean 7 9.9310 ( 0.00%) 10.8367 * -9.12%* 9.9910 ( -0.60%) : Amean 12 16.6577 ( 0.00%) 18.2363 * -9.48%* 17.1083 ( -2.71%) : Amean 18 26.5133 ( 0.00%) 27.8833 * -5.17%* 25.7663 ( 2.82%) : Amean 24 34.3003 ( 0.00%) 34.6830 ( -1.12%) 32.0450 ( 6.58%) : Amean 30 40.0063 ( 0.00%) 40.5800 ( -1.43%) 41.5087 ( -3.76%) : Amean 32 40.1407 ( 0.00%) 41.2273 ( -2.71%) 39.9417 ( 0.50%)
:
: It's showing that the vanilla kernel takes a hit (as the bisection : indicated it would) and that disabling PSI by default is reasonably : close in terms of performance for this particular workload on this : particular machine so;
--- .../admin-guide/kernel-parameters.txt | 4 +++ include/linux/psi.h | 3 +- init/Kconfig | 9 ++++++ kernel/sched/psi.c | 30 +++++++++++++------ kernel/sched/stats.h | 8 ++--- 5 files changed, 40 insertions(+), 14 deletions(-)
Documentation/admin-guide/kernel-parameters.txt +4 -0
@@ -3504,6 +3504,10 @@ before loading. See Documentation/blockdev/ramdisk.txt. + psi= [KNL] Enable or disable pressure stall information + tracking. + Format: <bool> + psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to probe for; one of (bare|imps|exps|lifebook|any). psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
include/linux/psi.h +2 -1
@@ -1,6 +1,7 @@#ifndef _LINUX_PSI_H#define _LINUX_PSI_H +#include <linux/jump_label.h> #include <linux/psi_types.h> #include <linux/sched.h>
@@ -9,7 +10,7 @@ struct css_set;#ifdef CONFIG_PSI -extern bool psi_disabled; +extern struct static_key_false psi_disabled;void psi_init (void );
init/Kconfig +9 -0
@@ -509,6 +509,15 @@ config PSI Say N if unsure. +config PSI_DEFAULT_DISABLED + bool "Require boot parameter to enable pressure stall information tracking" + default n + depends on PSI + help + If set, pressure stall information tracking will be disabled + per default but can be enabled through passing psi_enable=1 + on the kernel commandline during boot. + endmenu # "CPU/Task time and stats accounting" config CPU_ISOLATION
kernel/sched/psi.c +21 -9
@@ -136,8 +136,18 @@static int psi_bug__read_mostly ; -bool psi_disabled__read_mostly ; -core_param (psi_disabled, psi_disabled, bool,0644 ); +DEFINE_STATIC_KEY_FALSE (psi_disabled); + +#ifdef CONFIG_PSI_DEFAULT_DISABLED +bool psi_enable; +#else +bool psi_enable = true; +#endif +static int __init setup_psi (char *str) +{ +return kstrtobool (str, &psi_enable) ==0 ; +} +__setup ("psi=" , setup_psi);/* Running averages - we need to be higher-res than loadavg */ #define PSI_FREQ (2*HZ+1)/* 2 sec intervals */
@@ -169,8 +179,10 @@ static void group_init(struct psi_group *group)void __init psi_init (void ) { -if (psi_disabled) +if (!psi_enable) { +static_branch_enable (&psi_disabled);return ; + } psi_period =jiffies_to_nsecs (PSI_FREQ );group_init (&psi_system);
@@ -549,7 +561,7 @@ void psi_memstall_enter(unsigned long *flags)struct rq_flags rf;struct rq *rq; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ; *flags = current->flags &PF_MEMSTALL ;
@@ -579,7 +591,7 @@ void psi_memstall_leave(unsigned long *flags)struct rq_flags rf;struct rq *rq; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;if (*flags)
@@ -600,7 +612,7 @@ void psi_memstall_leave(unsigned long *flags)#ifdef CONFIG_CGROUPS int psi_cgroup_alloc (struct cgroup *cgroup) { -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return 0 ; cgroup->psi.pcpu = alloc_percpu(struct psi_group_cpu);
@@ -612,7 +624,7 @@ int psi_cgroup_alloc(struct cgroup *cgroup)void psi_cgroup_free (struct cgroup *cgroup) { -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;cancel_delayed_work_sync (&cgroup->psi.clock_work);
@@ -637,7 +649,7 @@ void cgroup_move_task(struct task_struct *task, struct css_set *to)struct rq_flags rf;struct rq *rq; -if (psi_disabled) { +if (static_branch_likely (&psi_disabled)) {/* * Lame to do this here, but the scheduler cannot be locked * from the outside, so we move cgroups from inside sched/.
@@ -673,7 +685,7 @@ int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res) {int full; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return -EOPNOTSUPP ;update_stats (group);
kernel/sched/stats.h +4 -4
@@ -66,7 +66,7 @@ static inline void psi_enqueue(struct task_struct *p, bool wakeup) {int clear =0 , set =TSK_RUNNING ; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;if (!wakeup || p->sched_psi_wake_requeue) {
@@ -86,7 +86,7 @@ static inline void psi_dequeue(struct task_struct *p, bool sleep) {int clear =TSK_RUNNING , set =0 ; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;if (!sleep) {
@@ -102,7 +102,7 @@ static inline void psi_dequeue(struct task_struct *p, bool sleep)static inline void psi_ttwu_dequeue (struct task_struct *p) { -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;/* * Is the task being migrated during a wakeup? Make sure to
@@ -128,7 +128,7 @@ static inline void psi_ttwu_dequeue(struct task_struct *p)static inline void psi_task_tick (struct rq *rq) { -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;if (unlikely (rq->curr->flags &PF_MEMSTALL ))
Signature · 1 line
2.19.1
Quoted 9 lines · Johannes Weiner
From
347b69a52d1ec7e71df1108cbc5703d6dd0616baMon Sep 17 00:00:00 2001
From: Johannes Weiner <[email protected]>
Date: Mon, 26 Nov 2018 09:39:23 -0500
Subject: [PATCH] psi: make disabling/enabling easier for vendor kernelsMel Gorman reports a hackbench regression with psi that would prohibit shipping the suse kernel with it default-enabled, but he'd still like users to be able to opt in at little to no cost to others.
Quoted 5 lines
With the current combination of
CONFIG_PSIand thepsi_disabledbool set from the commandline, this is a challenge. Do the following things to make it easier:1. Add a config option
CONFIG_PSI_DEFAULT_ENABLEDthat allows distros
This should be: CONFIG_PSI_DEFAULT_DISABLED
Refreshed the patch.
---
Quoted 1 line
From
dc1511101b4c6aa3f7cfb91d8634a682fe7c147eMon Sep 17 00:00:00 2001
From: Johannes Weiner <[email protected]>
Date: Mon, 26 Nov 2018 09:39:23 -0500
Subject: [PATCH] psi: make disabling/enabling easier for vendor kernels
Mel Gorman reports a hackbench regression with psi that would prohibit shipping the suse kernel with it default-enabled, but he'd still like users to be able to opt in at little to no cost to others.
With the current combination of CONFIG_PSI and the psi_disabled bool set from the commandline, this is a challenge. Do the following things to make it easier:
1. Add a config option CONFIG_PSI_DEFAULT_DISABLED that allows distros to enable CONFIG_PSI in their kernel but leave the feature disabled unless a user requests it at boot-time.
To avoid double negatives, rename psi_disabled= to psi=.
2. Make psi_disabled a static branch to eliminate any branch costs when the feature is disabled.
In terms of numbers before and after this patch, Mel says:
: The following is a comparision using CONFIG_PSI=n as a baseline against : your patch and a vanilla kernel
:
: 4.20.0-rc4 4.20.0-rc4 4.20.0-rc4
: kconfigdisable-v1r1 vanilla psidisable-v1r1 : Amean 1 1.3100 ( 0.00%) 1.3923 ( -6.28%) 1.3427 ( -2.49%) : Amean 3 3.8860 ( 0.00%) 4.1230 * -6.10%* 3.8860 ( -0.00%) : Amean 5 6.8847 ( 0.00%) 8.0390 * -16.77%* 6.7727 ( 1.63%) : Amean 7 9.9310 ( 0.00%) 10.8367 * -9.12%* 9.9910 ( -0.60%) : Amean 12 16.6577 ( 0.00%) 18.2363 * -9.48%* 17.1083 ( -2.71%) : Amean 18 26.5133 ( 0.00%) 27.8833 * -5.17%* 25.7663 ( 2.82%) : Amean 24 34.3003 ( 0.00%) 34.6830 ( -1.12%) 32.0450 ( 6.58%) : Amean 30 40.0063 ( 0.00%) 40.5800 ( -1.43%) 41.5087 ( -3.76%) : Amean 32 40.1407 ( 0.00%) 41.2273 ( -2.71%) 39.9417 ( 0.50%)
:
: It's showing that the vanilla kernel takes a hit (as the bisection : indicated it would) and that disabling PSI by default is reasonably : close in terms of performance for this particular workload on this : particular machine so;
--- .../admin-guide/kernel-parameters.txt | 4 +++ include/linux/psi.h | 3 +- init/Kconfig | 9 ++++++ kernel/sched/psi.c | 30 +++++++++++++------ kernel/sched/stats.h | 8 ++--- 5 files changed, 40 insertions(+), 14 deletions(-)
Documentation/admin-guide/kernel-parameters.txt +4 -0
@@ -3504,6 +3504,10 @@ before loading. See Documentation/blockdev/ramdisk.txt. + psi= [KNL] Enable or disable pressure stall information + tracking. + Format: <bool> + psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to probe for; one of (bare|imps|exps|lifebook|any). psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
include/linux/psi.h +2 -1
@@ -1,6 +1,7 @@#ifndef _LINUX_PSI_H#define _LINUX_PSI_H +#include <linux/jump_label.h> #include <linux/psi_types.h> #include <linux/sched.h>
@@ -9,7 +10,7 @@ struct css_set;#ifdef CONFIG_PSI -extern bool psi_disabled; +extern struct static_key_false psi_disabled;void psi_init (void );
init/Kconfig +9 -0
@@ -509,6 +509,15 @@ config PSI Say N if unsure. +config PSI_DEFAULT_DISABLED + bool "Require boot parameter to enable pressure stall information tracking" + default n + depends on PSI + help + If set, pressure stall information tracking will be disabled + per default but can be enabled through passing psi_enable=1 + on the kernel commandline during boot. + endmenu # "CPU/Task time and stats accounting" config CPU_ISOLATION
kernel/sched/psi.c +21 -9
@@ -136,8 +136,18 @@static int psi_bug__read_mostly ; -bool psi_disabled__read_mostly ; -core_param (psi_disabled, psi_disabled, bool,0644 ); +DEFINE_STATIC_KEY_FALSE (psi_disabled); + +#ifdef CONFIG_PSI_DEFAULT_DISABLED +bool psi_enable; +#else +bool psi_enable = true; +#endif +static int __init setup_psi (char *str) +{ +return kstrtobool (str, &psi_enable) ==0 ; +} +__setup ("psi=" , setup_psi);/* Running averages - we need to be higher-res than loadavg */ #define PSI_FREQ (2*HZ+1)/* 2 sec intervals */
@@ -169,8 +179,10 @@ static void group_init(struct psi_group *group)void __init psi_init (void ) { -if (psi_disabled) +if (!psi_enable) { +static_branch_enable (&psi_disabled);return ; + } psi_period =jiffies_to_nsecs (PSI_FREQ );group_init (&psi_system);
@@ -549,7 +561,7 @@ void psi_memstall_enter(unsigned long *flags)struct rq_flags rf;struct rq *rq; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ; *flags = current->flags &PF_MEMSTALL ;
@@ -579,7 +591,7 @@ void psi_memstall_leave(unsigned long *flags)struct rq_flags rf;struct rq *rq; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;if (*flags)
@@ -600,7 +612,7 @@ void psi_memstall_leave(unsigned long *flags)#ifdef CONFIG_CGROUPS int psi_cgroup_alloc (struct cgroup *cgroup) { -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return 0 ; cgroup->psi.pcpu = alloc_percpu(struct psi_group_cpu);
@@ -612,7 +624,7 @@ int psi_cgroup_alloc(struct cgroup *cgroup)void psi_cgroup_free (struct cgroup *cgroup) { -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;cancel_delayed_work_sync (&cgroup->psi.clock_work);
@@ -637,7 +649,7 @@ void cgroup_move_task(struct task_struct *task, struct css_set *to)struct rq_flags rf;struct rq *rq; -if (psi_disabled) { +if (static_branch_likely (&psi_disabled)) {/* * Lame to do this here, but the scheduler cannot be locked * from the outside, so we move cgroups from inside sched/.
@@ -673,7 +685,7 @@ int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res) {int full; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return -EOPNOTSUPP ;update_stats (group);
kernel/sched/stats.h +4 -4
@@ -66,7 +66,7 @@ static inline void psi_enqueue(struct task_struct *p, bool wakeup) {int clear =0 , set =TSK_RUNNING ; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;if (!wakeup || p->sched_psi_wake_requeue) {
@@ -86,7 +86,7 @@ static inline void psi_dequeue(struct task_struct *p, bool sleep) {int clear =TSK_RUNNING , set =0 ; -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;if (!sleep) {
@@ -102,7 +102,7 @@ static inline void psi_dequeue(struct task_struct *p, bool sleep)static inline void psi_ttwu_dequeue (struct task_struct *p) { -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;/* * Is the task being migrated during a wakeup? Make sure to
@@ -128,7 +128,7 @@ static inline void psi_ttwu_dequeue(struct task_struct *p)static inline void psi_task_tick (struct rq *rq) { -if (psi_disabled) +if (static_branch_likely (&psi_disabled))return ;if (unlikely (rq->curr->flags &PF_MEMSTALL ))
Signature · 1 line
2.19.1