Re: [LKP] [fs/locks] 83b381078b: will-it-scale.per_thread_ops -62.5% regression
From: J. Bruce Fields
Date: Tue Nov 27 2018 - 12:43:21 EST
Thanks for the report!
On Tue, Nov 27, 2018 at 02:01:02PM +0800, kernel test robot wrote:
> FYI, we noticed a -62.5% regression of will-it-scale.per_thread_ops due to commit:
>
>
> commit: 83b381078b5ecab098ebf6bc9548bb32af1dbf31 ("fs/locks: always delete_block after waiting.")
> https://git.kernel.org/cgit/linux/kernel/git/jlayton/linux.git locks-next
>
> in testcase: will-it-scale
> on test machine: 88 threads Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz with 64G memory
> with following parameters:
>
> nr_task: 16
> mode: thread
> test: lock1
So I guess it's doing this, uncontended file lock/unlock?:
https://github.com/antonblanchard/will-it-scale/blob/master/tests/lock1.c
Each thread is repeatedly locking and unlocking a file that is only used
by that thread.
By the way, what's the X-axis on these graphs? (Or the y-axis, for that
matter?)
--b.
> will-it-scale.per_thread_ops
>
> 450000 +-+----------------------------------------------------------------+
> | |
> 400000 +-+ +..+.. .+..+.. .+..+..+...+..+..+.. +.. .+.. ..|
> 350000 +-+ .. +. +. .. +. +..+ |
> | + + + : |
> 300000 +-+ : : |
> 250000 +-+ : : |
> | : : |
> 200000 +-+ : : |
> 150000 +-+ : : |
> O O O O O O O O O O O O O O O O O :O: O O O O O
> 100000 +-+ : : |
> 50000 +-+ : : |
> | : |
> 0 +-+----------------------------------------------------------------+
>
>
> will-it-scale.workload
>
> 7e+06 +-+-----------------------------------------------------------------+
> | +...+.. .+..+..+ + +.. |
> 6e+06 +-+ +..+.. .. .+..+..+. + + + .. ..|
> | .. + +. + + + + +..+ |
> 5e+06 +-++ + + : |
> | : : |
> 4e+06 +-+ : : |
> | : : |
> 3e+06 +-+ : : |
> | O O : : O O |
> 2e+06 O-+O O O O O O O O O O O O O O : O: O O O
> | : : |
> 1e+06 +-+ : : |
> | : |
> 0 +-+-----------------------------------------------------------------+
>
>
> will-it-scale.time.user_time
>
> 250 +-+-------------------------------------------------------------------+
> | .+.. .+.. +.. |
> |.. +...+.. .+. .+...+..+..+. +.. +.. .. . ..|
> 200 +-+ .. +. +. . .. + +..+ |
> | + + + : |
> | : : |
> 150 +-+ : : |
> | : : |
> 100 +-+ : : |
> | O O : : |
> O O O O O O O O O O O O O O O :O: O O O O O
> 50 +-+ : : |
> | : : |
> | : |
> 0 +-+-------------------------------------------------------------------+
>
>
> will-it-scale.time.system_time
>
> 5000 +-+------------------------------------------------------------------+
> 4500 O-+O..O..O...O..O..O..O..O..O..O...O..O..O..O..O..O O O...O..O..O..O
> | : : |
> 4000 +-+ : : |
> 3500 +-+ : : |
> | : : |
> 3000 +-+ : : |
> 2500 +-+ : : |
> 2000 +-+ : : |
> | : : |
> 1500 +-+ : : |
> 1000 +-+ : : |
> | : |
> 500 +-+ : |
> 0 +-+------------------------------------------------------------------+
>
>
> [*] bisect-good sample
> [O] bisect-bad sample