linux-kernel - Re: [lkp] [xfs] 68a9f5e700: aim7.jobs-per-min -13.6% regression

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Date:	Wed, 10 Aug 2016 11:24:16 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	kernel test robot <xiaolong.ye@...el.com>
Cc:	Christoph Hellwig <hch@....de>, Dave Chinner <david@...morbit.com>,
	Bob Peterson <rpeterso@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, LKP <lkp@...org>
Subject: Re: [lkp] [xfs] 68a9f5e700: aim7.jobs-per-min -13.6% regression

On Tue, Aug 9, 2016 at 7:33 AM, kernel test robot <xiaolong.ye@...el.com> wrote:
>
> FYI, we noticed a -13.6% regression of aim7.jobs-per-min due to commit:
> 68a9f5e7007c ("xfs: implement iomap based buffered write path")
>
> in testcase: aim7
> on test machine: 48 threads Ivytown Ivy Bridge-EP with 64G memory
> with following parameters:
>
>         disk: 1BRD_48G
>         fs: xfs
>         test: disk_wrt
>         load: 3000
>         cpufreq_governor: performance

Christop, Dave, was this expected?

>From looking at the numbers, it looks like much more IO going on (and
this less CPU load)..

>      37.23 ±  0%     +15.6%      43.04 ±  0%  aim7.time.elapsed_time
>      37.23 ±  0%     +15.6%      43.04 ±  0%  aim7.time.elapsed_time.max
>       6424 ±  1%     +31.3%       8432 ±  1%  aim7.time.involuntary_context_switches>       4003 ±  0%     +28.1%       5129 ±  1%  proc-vmstat.nr_active_file
>     979.25 ±  0%     +63.7%       1602 ±  1%  proc-vmstat.pgactivate
>       4699 ±  3%    +162.6%      12340 ± 73%  proc-vmstat.pgpgout
>      50.23 ± 19%     -27.3%      36.50 ± 17%  sched_debug.cpu.cpu_load[1].avg
>     466.50 ± 29%     -51.8%     225.00 ± 73%  sched_debug.cpu.cpu_load[1].max
>      77.78 ± 33%     -50.6%      38.40 ± 57%  sched_debug.cpu.cpu_load[1].stddev
>     300.50 ± 33%     -52.9%     141.50 ± 48%  sched_debug.cpu.cpu_load[2].max
>       1836 ± 10%     +65.5%       3039 ±  8%  slabinfo.scsi_data_buffer.active_objs
>       1836 ± 10%     +65.5%       3039 ±  8%  slabinfo.scsi_data_buffer.num_objs
>     431.75 ± 10%     +65.6%     715.00 ±  8%  slabinfo.xfs_efd_item.active_objs
>     431.75 ± 10%     +65.6%     715.00 ±  8%  slabinfo.xfs_efd_item.num_objs

but what do I know. Those profiles from the robot are pretty hard to
make sense of.

            Linus