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Message-ID: <87d1sb8s39.fsf@yhuang-dev.intel.com>
Date: Fri, 05 Feb 2016 16:43:54 +0800
From: "Huang\, Ying" <ying.huang@...ux.intel.com>
To: Willy Tarreau <w@....eu>
Cc: lkp@...org, LKML <linux-kernel@...r.kernel.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [lkp] [pipe] 759c01142a: -51.5% hackbench.throughput
kernel test robot <ying.huang@...ux.intel.com> writes:
> FYI, we noticed the below changes on
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> commit 759c01142a5d0f364a462346168a56de28a80f52 ("pipe: limit the per-user amount of pages allocated in pipes")
>
>
> =========================================================================================
> compiler/cpufreq_governor/ipc/kconfig/mode/nr_threads/rootfs/tbox_group/testcase:
> gcc-4.9/performance/pipe/x86_64-rhel/threads/1600%/debian-x86_64-2015-02-07.cgz/lkp-wsx02/hackbench
>
> commit:
> 558041d8d21b48287224dd0e32cf19563c77607c
> 759c01142a5d0f364a462346168a56de28a80f52
>
> 558041d8d21b4828 759c01142a5d0f364a46234616
> ---------------- --------------------------
> %stddev %change %stddev
> \ | \
> 219967 . 4% -51.5% 106583 . 1% hackbench.throughput
> 5.319e+08 . 11% -19.7% 4.273e+08 . 0% hackbench.time.involuntary_context_switches
> 2422668 . 9% -36.4% 1540731 . 2% hackbench.time.minor_page_faults
> 7127 . 11% +9.4% 7800 . 0% hackbench.time.percent_of_cpu_this_job_got
> 42924 . 9% +11.9% 48049 . 1% hackbench.time.system_time
> 1665 . 11% -49.3% 844.05 . 1% hackbench.time.user_time
> 534.25 . 55% +298.5% 2129 . 67% numa-meminfo.node3.AnonHugePages
> 8581 . 57% -48.4% 4427 . 1% uptime.idle
> 5705345 . 13% +58.8% 9061490 . 5% softirqs.RCU
> 279868 . 8% +20.4% 336916 . 1% softirqs.SCHED
> 26.75 . 23% +245.8% 92.50 . 39% vmstat.procs.b
> 9809 . 13% -64.7% 3463 . 7% vmstat.procs.r
> 284320 . 13% -45.9% 153686 . 1% vmstat.system.in
> 114.00 . 10% -50.9% 56.00 . 0% time.file_system_outputs
> 5.319e+08 . 11% -19.7% 4.273e+08 . 0% time.involuntary_context_switches
> 2422668 . 9% -36.4% 1540731 . 2% time.minor_page_faults
> 1665 . 11% -49.3% 844.05 . 1% time.user_time
> 89.86 . 10% +8.9% 97.84 . 0% turbostat.%Busy
> 2270 . 10% +8.9% 2471 . 0% turbostat.Avg_MHz
> 1.45 . 8% -52.6% 0.69 . 9% turbostat.CPU%c1
> 0.17 . 13% -52.2% 0.08 . 34% turbostat.CPU%c3
> 8.53 .116% -83.7% 1.39 . 3% turbostat.CPU%c6
> 63583716 . 16% -98.1% 1183913 . 53% numa-numastat.node0.local_node
> 63587769 . 16% -98.1% 1189061 . 53% numa-numastat.node0.numa_hit
> 69989955 . 6% -96.8% 2239323 . 8% numa-numastat.node1.local_node
> 69995282 . 6% -96.8% 2244474 . 8% numa-numastat.node1.numa_hit
> 56620071 . 22% -97.3% 1520012 . 32% numa-numastat.node2.local_node
> 56625301 . 22% -97.3% 1522594 . 31% numa-numastat.node2.numa_hit
> 63753303 . 22% -96.1% 2508634 . 14% numa-numastat.node3.local_node
> 63754612 . 22% -96.1% 2511213 . 14% numa-numastat.node3.numa_hit
> 32233121 . 15% -97.4% 830659 . 60% numa-vmstat.node0.numa_hit
> 32193958 . 15% -97.5% 790185 . 63% numa-vmstat.node0.numa_local
> 35020615 . 10% -96.4% 1253289 . 8% numa-vmstat.node1.numa_hit
> 34968563 . 10% -96.6% 1201078 . 9% numa-vmstat.node1.numa_local
> 30394713 . 14% -97.2% 843134 . 31% numa-vmstat.node2.numa_hit
> 30373607 . 14% -97.3% 824676 . 31% numa-vmstat.node2.numa_local
> 32334081 . 21% -95.5% 1469250 . 16% numa-vmstat.node3.numa_hit
> 32286373 . 21% -95.6% 1420300 . 16% numa-vmstat.node3.numa_local
> 1.868e+08 . 11% -51.0% 91569694 . 13% cpuidle.C1-NHM.time
> 1743049 . 10% -34.6% 1139878 . 11% cpuidle.C1-NHM.usage
> 1.918e+08 . 12% -49.7% 96433830 . 11% cpuidle.C1E-NHM.time
> 1243978 . 16% -40.7% 738168 . 12% cpuidle.C1E-NHM.usage
> 70404853 . 8% -47.4% 37040591 . 19% cpuidle.C3-NHM.time
> 4.723e+09 .108% -81.6% 8.672e+08 . 3% cpuidle.C6-NHM.time
> 311666 . 18% -47.9% 162252 . 15% cpuidle.C6-NHM.usage
> 2.456e+08 . 18% -53.2% 1.15e+08 . 9% cpuidle.POLL.time
> 260576 . 21% -58.6% 107765 . 17% cpuidle.POLL.usage
> 906770 . 8% -19.4% 730530 . 5% proc-vmstat.numa_hint_faults
> 2.54e+08 . 11% -97.1% 7464740 . 4% proc-vmstat.numa_hit
> 2.539e+08 . 11% -97.1% 7449281 . 4% proc-vmstat.numa_local
> 662291 . 10% -33.4% 441016 . 5% proc-vmstat.numa_pages_migrated
> 1203460 . 6% -16.7% 1002984 . 5% proc-vmstat.numa_pte_updates
> 5716982 . 17% -97.2% 158482 . 40% proc-vmstat.pgalloc_dma32
> 2.521e+08 . 11% -96.3% 9338972 . 3% proc-vmstat.pgalloc_normal
> 3627983 . 4% -26.1% 2682860 . 1% proc-vmstat.pgfault
> 2.576e+08 . 11% -96.4% 9352801 . 3% proc-vmstat.pgfree
> 662291 . 10% -33.4% 441016 . 5% proc-vmstat.pgmigrate_success
> 27845 . 11% -79.8% 5624 . 1% slabinfo.kmalloc-1024.active_objs
> 879.00 . 11% -79.2% 183.00 . 1% slabinfo.kmalloc-1024.active_slabs
> 28142 . 11% -79.1% 5879 . 0% slabinfo.kmalloc-1024.num_objs
> 879.00 . 11% -79.2% 183.00 . 1% slabinfo.kmalloc-1024.num_slabs
> 20288 . 0% +129.9% 46639 . 0% slabinfo.kmalloc-64.active_objs
> 317.00 . 0% +131.4% 733.50 . 0% slabinfo.kmalloc-64.active_slabs
> 20288 . 0% +131.6% 46980 . 0% slabinfo.kmalloc-64.num_objs
> 317.00 . 0% +131.4% 733.50 . 0% slabinfo.kmalloc-64.num_slabs
> 335.50 . 9% -44.8% 185.25 . 4% slabinfo.taskstats.active_objs
> 335.50 . 9% -44.8% 185.25 . 4% slabinfo.taskstats.num_objs
> 38.97 . 29% +51.7% 59.11 . 7% perf-profile.cycles-pp.__account_scheduler_latency.enqueue_entity.enqueue_task_fair.activate_task.ttwu_do_activate
> 39.95 . 28% +53.0% 61.10 . 7% perf-profile.cycles-pp.ttwu_do_activate.constprop.86.try_to_wake_up.default_wake_function.autoremove_wake_function.__wake_up_common
>From above perf profile output,
Most time is spent for __account_scheduler_latency, which is part of
latency-stats (latencytop) utility to collect system latency statistics.
It uses a global spinlock (latency_lock) to protect its data structure,
the latency_lock becomes the bottleneck of the test. The increased
context switches after the commit increases the contention of
latency_lock, so cause the regression. After disable latency-stats, the
performance improved instead of regressed. The compare result is as
follow:
=========================================================================================
compiler/cpufreq_governor/debug-setup/ipc/kconfig/mode/nr_threads/rootfs/tbox_group/testcase:
gcc-4.9/performance/no-latency_stats/pipe/x86_64-rhel/threads/1600%/debian-x86_64-2015-02-07.cgz/lkp-wsx02/hackbench
commit:
558041d8d21b48287224dd0e32cf19563c77607c
759c01142a5d0f364a462346168a56de28a80f52
558041d8d21b4828 759c01142a5d0f364a46234616
---------------- --------------------------
fail:runs %reproduction fail:runs
| | |
1:6 -17% :4 last_state.is_incomplete_run
%stddev %change %stddev
\ | \
251067 ± 4% +53.2% 384708 ± 0% hackbench.throughput
1.468e+09 ± 6% -51.6% 7.099e+08 ± 40% hackbench.time.involuntary_context_switches
7299 ± 4% -49.0% 3725 ± 57% hackbench.time.percent_of_cpu_this_job_got
42840 ± 3% -33.3% 28582 ± 38% hackbench.time.system_time
I think the performance improvement comes from the decreased the cache
miss rate, because of the decreased working set, which comes from the
decreased pipe size, as follow,
7.478e+09 ± 4% -54.8% 3.38e+09 ± 36% perf-stat.LLC-load-misses
2.087e+11 ± 3% -3.6% 2.012e+11 ± 37% perf-stat.LLC-loads
1.605e+10 ± 3% -76.5% 3.771e+09 ± 37% perf-stat.LLC-store-misses
6.751e+10 ± 2% -11.7% 5.963e+10 ± 36% perf-stat.LLC-stores
The store miss rate decreased from about 23.77% to 6.32%.
Best Regards,
Huang, Ying
> 3.89 . 60% +334.7% 16.93 . 13% perf-profile.cycles-pp.__vfs_read.vfs_read.sys_read.entry_SYSCALL_64_fastpath
> 0.70 . 30% +1969.3% 14.49 . 11% perf-profile.cycles-pp.__wake_up_common.__wake_up_sync_key.pipe_read.__vfs_read.vfs_read
> 0.71 . 30% +1971.0% 14.65 . 11% perf-profile.cycles-pp.__wake_up_sync_key.pipe_read.__vfs_read.vfs_read.sys_read
> 0.69 . 84% -92.3% 0.05 . 63% perf-profile.cycles-pp._raw_spin_lock.__schedule.schedule.exit_to_usermode_loop.syscall_return_slowpath
> 34.58 . 33% +57.1% 54.33 . 7% perf-profile.cycles-pp._raw_spin_lock_irqsave.__account_scheduler_latency.enqueue_entity.enqueue_task_fair.activate_task
> 39.61 . 28% +53.7% 60.89 . 7% perf-profile.cycles-pp.activate_task.ttwu_do_activate.try_to_wake_up.default_wake_function.autoremove_wake_function
> 0.70 . 30% +1967.9% 14.47 . 11% perf-profile.cycles-pp.autoremove_wake_function.__wake_up_common.__wake_up_sync_key.pipe_read.__vfs_read
> 0.70 . 30% +1965.0% 14.46 . 11% perf-profile.cycles-pp.default_wake_function.autoremove_wake_function.__wake_up_common.__wake_up_sync_key.pipe_read
> 38.99 . 28% +54.5% 60.25 . 7% perf-profile.cycles-pp.enqueue_entity.enqueue_task_fair.activate_task.ttwu_do_activate.try_to_wake_up
> 39.45 . 28% +53.9% 60.72 . 7% perf-profile.cycles-pp.enqueue_task_fair.activate_task.ttwu_do_activate.try_to_wake_up.default_wake_function
> 57.97 . 20% +40.4% 81.35 . 8% perf-profile.cycles-pp.entry_SYSCALL_64_fastpath
> 1.31 . 60% -92.0% 0.10 . 67% perf-profile.cycles-pp.native_queued_spin_lock_slowpath._raw_spin_lock.__schedule.schedule.exit_to_usermode_loop
> 2.54 . 68% -81.8% 0.46 . 60% perf-profile.cycles-pp.native_queued_spin_lock_slowpath._raw_spin_lock.try_to_wake_up.default_wake_function.autoremove_wake_function
> 34.38 . 33% +55.7% 53.54 . 6% perf-profile.cycles-pp.native_queued_spin_lock_slowpath._raw_spin_lock_irqsave.__account_scheduler_latency.enqueue_entity.enqueue_task_fair
> 3.67 . 65% +354.5% 16.69 . 11% perf-profile.cycles-pp.pipe_read.__vfs_read.vfs_read.sys_read.entry_SYSCALL_64_fastpath
> 5.22 . 42% +250.6% 18.30 . 21% perf-profile.cycles-pp.sys_read.entry_SYSCALL_64_fastpath
> 39.95 . 28% +53.0% 61.10 . 7% perf-profile.cycles-pp.ttwu_do_activate.constprop.86.try_to_wake_up.default_wake_function.autoremove_wake_function.__wake_up_common
> 4.70 . 48% +282.5% 17.96 . 19% perf-profile.cycles-pp.vfs_read.sys_read.entry_SYSCALL_64_fastpath
> 16323355 . 13% -100.0% 0.00 . -1% latency_stats.avg.nfs_wait_on_request.nfs_updatepage.nfs_write_end.generic_perform_write.__generic_file_write_iter.generic_file_write_iter.nfs_file_write.__vfs_write.vfs_write.SyS_write.entry_SYSCALL_64_fastpath
> 1702613 . 26% +288.1% 6607185 . 61% latency_stats.avg.pipe_read.__vfs_read.vfs_read.SyS_read.entry_SYSCALL_64_fastpath
> 31.67 . 74% +63999.7% 20298 .149% latency_stats.avg.stop_two_cpus.migrate_swap.task_numa_migrate.numa_migrate_preferred.task_numa_fault.handle_mm_fault.__do_page_fault.do_page_fault.page_fault
> 3607008 .163% -100.0% 384.25 . 14% latency_stats.avg.wait_on_page_bit.__filemap_fdatawait_range.filemap_fdatawait_range.filemap_write_and_wait_range.nfs4_file_fsync.[nfsv4].vfs_fsync_range.vfs_fsync.nfs4_file_flush.[nfsv4].filp_close.do_dup2.SyS_dup2.entry_SYSCALL_64_fastpath
> 1042512 . 15% +145.7% 2561649 . 35% latency_stats.avg.wait_on_page_bit.__migration_entry_wait.migration_entry_wait.handle_mm_fault.__do_page_fault.do_page_fault.page_fault
> 384229 . 2% -76.9% 88748 . 24% latency_stats.hits.call_rwsem_down_read_failed.do_exit.SyS_exit.entry_SYSCALL_64_fastpath
[snip]
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