filtered wakeups respun
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- v1 Latest2 of 3 patches 3 repliesIn review
2 of 3 patches are in this archive. The cover letter announces 3.
Patches in v1 No applies recorded yet
| # | Subject and files | Size | Replies | Applied |
|---|---|---|---|---|
| 2/3 | filtered buffer_head wakeupsfs/ fs/ include/ | +27 | 0 replies | |
| 3/3 | wake-one PG_locked/BH_Lock semanticsfs/ include/ include/ +2 more | +66 | 2 replies |
Reviews trailers per patch
No Reviewed-by, Acked-by or Tested-by trailers for v1 yet.
Cover letter [0/3] filtered wakeups respun
[1/3]: filtered wakeups
filter wakeups by the page being woken up for
[2/3]: filtered buffers
filter wakeups by the bh being woken up for
[3/3]: wakeone
restore wake-one semantics to bitlocking for pages and bh's
Same machine/etc. as before, except this time, ext3 instead of ext2. ext3 shows noise-level differences in raw throughputs with large reductions in cpu overhead, mostly on the read side.
ext2 results differ from these in that a 23% boost to sequential write cpu efficiency (throughput scaled by %cpu) is also achieved for sequential writes, almost entirely due to wake-one semantics. The tests take long enough to run that I've not done the ext2 results on a precisely-matching codebase. From the extant ext2 results:
$ cat ~/tmp/virgin_mm.log/tiotest.log Tiotest results for 512 concurrent io threads: ,----------------------------------------------------------------------. | Item | Time | Rate | Usr CPU | Sys CPU | +-----------------------+----------+--------------+----------+---------+ | Write 16384 MBs | 1118.1 s | 14.654 MB/s | 1.6 % | 280.9 % | | Random Write 2000 MBs | 336.2 s | 5.950 MB/s | 0.8 % | 20.4 % | | Read 16384 MBs | 1717.1 s | 9.542 MB/s | 1.4 % | 31.8 % | | Random Read 2000 MBs | 465.2 s | 4.300 MB/s | 1.1 % | 36.1 % | `----------------------------------------------------------------------' $ cat ~/tmp/filtered_wakeup.log/tiotest.log Tiotest results for 512 concurrent io threads: ,----------------------------------------------------------------------. | Item | Time | Rate | Usr CPU | Sys CPU | +-----------------------+----------+--------------+----------+---------+ | Write 16384 MBs | 1099.5 s | 14.901 MB/s | 2.2 % | 279.3 % | | Random Write 2000 MBs | 333.8 s | 5.991 MB/s | 1.0 % | 14.9 % | | Read 16384 MBs | 1706.3 s | 9.602 MB/s | 1.4 % | 19.1 % | | Random Read 2000 MBs | 460.3 s | 4.345 MB/s | 1.1 % | 14.8 % | `----------------------------------------------------------------------' $ cat ~/tmp/wakeone.log/tiotest.log Tiotest results for 512 concurrent io threads: ,----------------------------------------------------------------------. | Item | Time | Rate | Usr CPU | Sys CPU | +-----------------------+----------+--------------+----------+---------+ | Write 16384 MBs | 1073.8 s | 15.258 MB/s | 1.5 % | 237.3 % | | Random Write 2000 MBs | 336.9 s | 5.937 MB/s | 0.9 % | 15.2 % | | Read 16384 MBs | 1703.0 s | 9.621 MB/s | 1.3 % | 18.8 % | | Random Read 2000 MBs | 458.6 s | 4.361 MB/s | 1.0 % | 14.9 % | `----------------------------------------------------------------------'
/home/wli/tmp/virgin_mm.log/tiotest.log:
Write: 5.1873MB/cpusec Random Write: 28.0660MB/cpusec Read: 28.7410MB/cpusec Random Read: 11.5591MB/cpusec /home/wli/tmp/filtered_wakeup.log/tiotest.log: Write: 5.2934MB/cpusec Random Write: 37.6792MB/cpusec Read: 46.8390MB/cpusec Random Read: 27.3270MB/cpusec /home/wli/tmp/wakeone.log/tiotest.log: Write: 6.3894MB/cpusec Random Write: 36.8758MB/cpusec Read: 47.8657MB/cpusec Random Read: 27.4277MB/cpusec
The wakeone implementation used for the ext2 run(s) above was somewhat less refined than the current one in that it didn't implement wake-one semantics for lock_buffer() and committed a major stupidity in waking more waiters than necessary in its wake_up_filtered().
One should also note specific complaints about random read performance are going around, and this near triples ext3's cpu efficiency on random reads i.e. it takes ext3 from 10.3MB/cpusec to 28.5MB/cpusec.
ext3 results;
before:
Tiotest results for 512 concurrent io threads:
,----------------------------------------------------------------------.
| Item | Time | Rate | Usr CPU | Sys CPU | +-----------------------+----------+--------------+----------+---------+ | Write 16384 MBs | 926.5 s | 17.683 MB/s | 1.9 % | 161.3 % | | Random Write 2000 MBs | 333.5 s | 5.998 MB/s | 0.9 % | 21.0 % | | Read 16384 MBs | 1634.0 s | 10.027 MB/s | 1.5 % | 28.4 % | | Random Read 2000 MBs | 448.1 s | 4.463 MB/s | 1.2 % | 42.2 % |
`----------------------------------------------------------------------'
Throughput scaled by cpu consumption:
Write: 10.8352MB/cpusec Random Write: 27.3881MB/cpusec Read: 33.5351MB/cpusec Random Read: 10.2834MB/cpusec
top 10 cpu consumers:
15328 finish_task_switch 79.8333
10149 __wake_up 158.5781
9859 generic_file_aio_write_nolock 4.3393
8836 file_read_actor 39.4464 7601 __do_softirq 26.3924 3114 kmem_cache_free 24.3281 2810 __find_get_block 9.7569 2727 prepare_to_wait 21.3047 2464 kmem_cache_alloc 19.2500 1675 tl0_linux32 52.3438
top 10 scheduler callers:
8827430 wait_on_page_bit 30650.7986
327735 __wait_on_buffer 1463.1027 209926 __handle_preemption 13120.3750 138613 worker_thread 254.8033
35838 generic_file_aio_write_nolock 15.7738
32265 __lock_page 112.0312
16281 pipe_wait 127.1953
9538 do_exit 9.3145
7622 shrink_list 4.1067
6816 compat_sys_nanosleep 17.7500
after:
Tiotest results for 512 concurrent io threads:
,----------------------------------------------------------------------.
| Item | Time | Rate | Usr CPU | Sys CPU | +-----------------------+----------+--------------+----------+---------+ | Write 16384 MBs | 926.7 s | 17.680 MB/s | 1.9 % | 140.4 % | | Random Write 2000 MBs | 334.4 s | 5.981 MB/s | 0.9 % | 19.7 % | | Read 16384 MBs | 1649.8 s | 9.931 MB/s | 1.3 % | 19.0 % | | Random Read 2000 MBs | 443.6 s | 4.509 MB/s | 1.1 % | 14.7 % |
`----------------------------------------------------------------------'
Throughput scaled by cpu consumption:
Write: 12.4245MB/cpusec Random Write: 29.0340MB/cpusec Read: 48.9212MB/cpusec Random Read: 28.5380MB/cpusec
top 10 cpu consumers:
9751 generic_file_aio_write_nolock 4.2918
9116 file_read_actor 40.6964 7419 __do_softirq 25.7604 5217 finish_task_switch 27.1719 3482 __find_get_block 12.0903 2725 kmem_cache_free 21.2891 2669 wake_up_filtered 13.9010 2543 kmem_cache_alloc 19.8672 1629 find_get_page 16.9688 1613 tl0_linux32 50.4062
top 10 scheduler callers:
2402700 wait_on_page_bit 6825.8523
198357 __handle_preemption 12397.3125
179318 worker_thread 329.6287
18343 generic_file_aio_write_nolock 8.0735
15687 pipe_wait 122.5547
9306 do_exit 9.0879
7531 __lock_buffer 39.2240 6814 compat_sys_nanosleep 17.7448 6716 kswapd 29.9821
5429 sys_wait4 9.4253
-- wli