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Date:   Tue, 5 Dec 2017 13:57:47 +0800
From:   Aaron Lu <aaron.lu@...el.com>
To:     Benjamin Coddington <bcodding@...hat.com>
Cc:     lkp@...org, Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Jeff Layton <jlayton@...hat.com>, xiaolong.ye@...el.com
Subject: Re: [LKP] [lkp-robot] [fs/locks] 52306e882f:
 stress-ng.lockofd.ops_per_sec -11% regression

On Wed, Nov 08, 2017 at 03:22:33PM +0800, Aaron Lu wrote:
> On Thu, Sep 28, 2017 at 04:02:23PM +0800, kernel test robot wrote:
> > 
> > Greeting,
> > 
> > FYI, we noticed a -11% regression of stress-ng.lockofd.ops_per_sec due to commit:
> > 
> > 
> > commit: 52306e882f77d3fd73f91435c41373d634acc5d2 ("fs/locks: Use allocation rather than the stack in fcntl_getlk()")
> > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> 
> It's been a while, I wonder what do you think of this regression?
> 
> The test stresses byte-range locks AFAICS and since the commit uses
> dynamic allocation instead of stack for the 'struct file_lock', it sounds
> natural the performance regressed for this test.
> 
> Now the question is, do we care about the performance regression here?

Appreciated it if you can share your opinion on this, thanks.

Regards,
Aaron
 
> Feel free to let me know if you need any other data.
> 
> Thanks for your time.
> 
> > in testcase: stress-ng
> > on test machine: 88 threads Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz with 128G memory
> > with following parameters:
> > 
> > 	testtime: 1s
> > 	class: filesystem
> > 	cpufreq_governor: performance
> > 
> > 
> > 
> > 
> > Details are as below:
> > -------------------------------------------------------------------------------------------------->
> > 
> > 
> > To reproduce:
> > 
> >         git clone https://github.com/intel/lkp-tests.git
> >         cd lkp-tests
> >         bin/lkp install job.yaml  # job file is attached in this email
> >         bin/lkp run     job.yaml
> > 
> > testcase/path_params/tbox_group/run: stress-ng/1s-filesystem-performance/lkp-bdw-ep6
> > 
> >        v4.13-rc1  52306e882f77d3fd73f91435c4  
> > ----------------  --------------------------  
> >          %stddev      change         %stddev
> >              \          |                \  
> >  1.219e+08             -11%   1.09e+08        stress-ng.lockofd.ops_per_sec
> >  1.229e+08             -10%  1.103e+08        stress-ng.locka.ops_per_sec
> >  1.233e+08             -10%  1.105e+08        stress-ng.locka.ops
> >  1.223e+08             -11%  1.093e+08        stress-ng.lockofd.ops
> >    1061237              10%    1168476        stress-ng.eventfd.ops
> >    1061205              10%    1168414        stress-ng.eventfd.ops_per_sec
> >    2913174               9%    3163165        stress-ng.time.voluntary_context_switches
> >      89.90              -4%      86.58        stress-ng.time.user_time
> >      26510              -6%      24822        stress-ng.io.ops
> >      26489              -6%      24798        stress-ng.io.ops_per_sec
> >     885499 ± 14%        18%    1042236        perf-stat.cpu-migrations
> >  2.537e+08              10%  2.783e+08        perf-stat.node-store-misses
> >    1067830 ±  4%         8%    1154877 ±  3%  perf-stat.page-faults
> >    5384755 ±  4%         7%    5747689        perf-stat.context-switches
> >      32.28               7%      34.42 ±  3%  perf-stat.node-store-miss-rate%
> >      12245 ±110%     -7e+03       5367 ± 29%  latency_stats.avg.call_usermodehelper_exec.__request_module.get_fs_type.do_mount.SyS_mount.entry_SYSCALL_64_fastpath
> >     311261 ±173%     -3e+05      11702 ±100%  latency_stats.avg.tty_release_struct.tty_release.__fput.____fput.task_work_run.exit_to_usermode_loop.syscall_return_slowpath.entry_SYSCALL_64_fastpath
> >       1472 ± 60%      4e+03       5144 ± 97%  latency_stats.max.sync_inodes_sb.sync_inodes_one_sb.iterate_supers.sys_sync.entry_SYSCALL_64_fastpath
> >        225 ± 39%      3e+03       3698 ±132%  latency_stats.max.rpc_wait_bit_killable.__rpc_wait_for_completion_task.nfs4_do_close.[nfsv4].__nfs4_close.[nfsv4].nfs4_close_sync.[nfsv4].nfs4_close_context.[nfsv4].__put_nfs_open_context.nfs_file_clear_open_context.nfs_file_release.__fput.____fput.task_work_run
> >        228 ± 34%      3e+03       3103 ±159%  latency_stats.max.rpc_wait_bit_killable.__rpc_wait_for_completion_task.nfs4_run_open_task.[nfsv4].nfs4_do_open.[nfsv4].nfs4_atomic_open.[nfsv4].nfs4_file_open.[nfsv4].do_dentry_open.vfs_open.path_openat.do_filp_open.do_sys_open.SyS_open
> >        270 ± 24%      3e+03       3110 ±162%  latency_stats.max.io_schedule.wait_on_page_bit_common.__filemap_fdatawait_range.filemap_write_and_wait_range.nfs_file_fsync.vfs_fsync_range.vfs_fsync.nfs4_file_flush.[nfsv4].filp_close.do_dup2.SyS_dup2.entry_SYSCALL_64_fastpath
> >      12245 ±110%     -7e+03       5367 ± 29%  latency_stats.max.call_usermodehelper_exec.__request_module.get_fs_type.do_mount.SyS_mount.entry_SYSCALL_64_fastpath
> >     927506 ±173%     -9e+05      11702 ±100%  latency_stats.max.tty_release_struct.tty_release.__fput.____fput.task_work_run.exit_to_usermode_loop.syscall_return_slowpath.entry_SYSCALL_64_fastpath
> >       7892 ± 54%      3e+04      33793 ±131%  latency_stats.sum.sync_inodes_sb.sync_inodes_one_sb.iterate_supers.sys_sync.entry_SYSCALL_64_fastpath
> >      12030 ±109%      2e+04      33536 ±136%  latency_stats.sum.autofs4_wait.autofs4_mount_wait.autofs4_d_manage.follow_managed.lookup_fast.path_openat.do_filp_open.do_sys_open.SyS_open.entry_SYSCALL_64_fastpath
> >      14311 ± 15%      7e+03      21729 ±116%  latency_stats.sum.call_rwsem_down_read_failed.page_lock_anon_vma_read.rmap_walk_anon.rmap_walk.try_to_unmap.migrate_pages.migrate_misplaced_page.__handle_mm_fault.handle_mm_fault.__do_page_fault.do_page_fault.page_fault
> >       8095 ± 22%      7e+03      15421 ± 79%  latency_stats.sum.call_rwsem_down_read_failed.rmap_walk_anon.rmap_walk.remove_migration_ptes.migrate_pages.migrate_misplaced_page.__handle_mm_fault.handle_mm_fault.__do_page_fault.do_page_fault.page_fault
> >        495 ± 39%      7e+03       7470 ±131%  latency_stats.sum.rpc_wait_bit_killable.__rpc_wait_for_completion_task.nfs4_do_close.[nfsv4].__nfs4_close.[nfsv4].nfs4_close_sync.[nfsv4].nfs4_close_context.[nfsv4].__put_nfs_open_context.nfs_file_clear_open_context.nfs_file_release.__fput.____fput.task_work_run
> >       3449 ± 18%      7e+03      10001 ± 68%  latency_stats.sum.io_schedule.wait_on_page_bit_common.__filemap_fdatawait_range.filemap_fdatawait_keep_errors.sync_inodes_sb.sync_inodes_one_sb.iterate_supers.sys_sync.entry_SYSCALL_64_fastpath
> >        378 ±123%      6e+03       6438 ±109%  latency_stats.sum.io_schedule.__lock_page.find_lock_entry.shmem_getpage_gfp.shmem_fault.__do_fault.__handle_mm_fault.handle_mm_fault.__do_page_fault.do_page_fault.page_fault
> >        386 ± 34%      3e+03       3242 ±153%  latency_stats.sum.rpc_wait_bit_killable.__rpc_wait_for_completion_task.nfs4_run_open_task.[nfsv4].nfs4_do_open.[nfsv4].nfs4_atomic_open.[nfsv4].nfs4_file_open.[nfsv4].do_dentry_open.vfs_open.path_openat.do_filp_open.do_sys_open.SyS_open
> >        413 ± 19%      3e+03       3256 ±156%  latency_stats.sum.io_schedule.wait_on_page_bit_common.__filemap_fdatawait_range.filemap_write_and_wait_range.nfs_file_fsync.vfs_fsync_range.vfs_fsync.nfs4_file_flush.[nfsv4].filp_close.do_dup2.SyS_dup2.entry_SYSCALL_64_fastpath
> >       2874 ±173%     -3e+03          0        latency_stats.sum.call_rwsem_down_write_failed.do_unlinkat.SyS_unlink.entry_SYSCALL_64_fastpath
> >       3683 ±172%     -4e+03          5 ±100%  latency_stats.sum.call_rwsem_down_read_failed.lookup_slow.walk_component.path_lookupat.filename_lookup.user_path_at_empty.SyS_chmod.entry_SYSCALL_64_fastpath
> >      12245 ±110%     -7e+03       5367 ± 29%  latency_stats.sum.call_usermodehelper_exec.__request_module.get_fs_type.do_mount.SyS_mount.entry_SYSCALL_64_fastpath
> >       7320 ±136%     -7e+03          0        latency_stats.sum.call_rwsem_down_write_failed.do_truncate.do_sys_ftruncate.SyS_ftruncate.entry_SYSCALL_64_fastpath
> >      52297 ±124%     -3e+04      26320 ± 16%  latency_stats.sum.call_rwsem_down_read_failed.lookup_slow.walk_component.link_path_walk.path_parentat.filename_parentat.do_unlinkat.SyS_unlink.entry_SYSCALL_64_fastpath
> >      64452 ± 83%     -3e+04      31383 ± 30%  latency_stats.sum.call_rwsem_down_write_failed.do_rmdir.SyS_rmdir.entry_SYSCALL_64_fastpath
> >    1867567 ±173%     -2e+06      11702 ±100%  latency_stats.sum.tty_release_struct.tty_release.__fput.____fput.task_work_run.exit_to_usermode_loop.syscall_return_slowpath.entry_SYSCALL_64_fastpath
> > 
> > 
> > 
> > 
> > Disclaimer:
> > Results have been estimated based on internal Intel analysis and are provided
> > for informational purposes only. Any difference in system hardware or software
> > design or configuration may affect actual performance.
> > 
> > 
> > Thanks,
> > Xiaolong

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