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Date:	Fri, 20 Jun 2014 00:28:42 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com>
Cc:	Jet Chen <jet.chen@...el.com>, LKML <linux-kernel@...r.kernel.org>,
	lkp@...org, Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [tracing] 939c7a4f04f: -46.4% cpuidle.C3-IVT.time

Hi Yoshihiro,

On Thu, Jun 19, 2014 at 03:04:22PM +0900, Yoshihiro YUNOMAE wrote:
> Hi Jet,
> 
> Thank you for your report.
> I have some questions for your test.
> 
> 1. Did you enable ftrace?

Yes, ftrace is enabled. Attached is the kernel config.

> This patch added a feature for ftrace. If you disabled ftrace in
> this test, my patch will not affect the system. Moreover, in my patch,
> arrays for saved_cmdlines were just changed from using static global
> variables to using kmalloc() on default setting. So, even if you enabled
> ftrace, this patch will not induce a big problem, I think.

Agreed, the patch itself looks good. Unfortunately sometimes a small
change in one place may lead to subtle changes in other places due to
data alignment etc. effects.

> 2. How did you test it and what does the result mean?
> Please tell me the workload, how to calculate the score,
> system settings, etc...

Workload is aim7's brk_test case, running on an Ivy Bridge-EX machine.
However it's not aim7's throughput that's regressed, but there are
changes in the C3 state, number of RCU softirqs and power consumption
etc.

Thanks,
Fengguang


> Thanks,
> Yoshihiro YUNOMAE
> 
> (2014/06/18 12:15), Jet Chen wrote:
> >Hi Yoshihiro,
> >
> >FYI, we noticed the below changes on
> >
> >commit 939c7a4f04fcd2162109744e8bf88194948a6e65 ("tracing: Introduce
> >saved_cmdlines_size file")
> >
> >test case: brickland3/aim7/3000-brk_test
> >
> >beba4bb096201ce  939c7a4f04fcd2162109744e8
> >---------------  -------------------------
> >     352643 ~40%     -46.4%     189136 ~15%  TOTAL cpuidle.C3-IVT.time
> >        750 ~ 2%     -13.3%        650 ~ 2%  TOTAL vmstat.procs.b
> >     362016 ~ 3%      -6.0%     340296 ~ 3%  TOTAL
> >proc-vmstat.pgmigrate_success
> >     362016 ~ 3%      -6.0%     340296 ~ 3%  TOTAL
> >proc-vmstat.numa_pages_migrated
> >    1642328 ~ 3%     +13.3%    1860721 ~ 2%  TOTAL softirqs.RCU
> >    2278829 ~ 2%     -14.0%    1959647 ~ 2%  TOTAL
> >time.voluntary_context_switches
> >        207 ~ 0%     -10.4%        185 ~ 0%  TOTAL time.user_time
> >             ~ 0%      +8.5%            ~ 0%  TOTAL turbostat.RAM_W
> >    4418246 ~ 3%      -6.4%    4136447 ~ 1%  TOTAL time.minor_page_faults
> >            ~ 0%      +3.4%            ~ 0%  TOTAL turbostat.Cor_W
> >            ~ 0%      +3.0%            ~ 0%  TOTAL turbostat.Pkg_W
> >   11354889 ~ 0%      +2.0%   11579897 ~ 0%  TOTAL
> >time.involuntary_context_switches
> >
> >Legend:
> >     ~XX%    - stddev percent
> >     [+-]XX% - change percent
> >
> >
> >                             time.voluntary_context_switches
> >
> >   2.4e+06
> >++---------------------------------------------------*------------+
> >           *..                         *..                    ..
> >..         |
> >   2.3e+06 ++      .*..          *.. ..
> >*               |
> >           |  *..*.    .  .*.. ..   *     *..               +
> >*..   *..*
> >           |            *.    *              .     .*..*.. +
> >..   |
> >   2.2e+06 ++                                 *..*.       *
> >*     |
> >
> >|                                                                 |
> >   2.1e+06
> >++                                                                |
> >
> >|                                                                 |
> >     2e+06 O+                                 O           O
> >O     |
> >           |                     O     O                     O
> >O        |
> >           |        O   O  O  O
> >O                           |
> >   1.9e+06 ++ O  O                                  O
> >O            |
> >           |                        O     O
> >O                     |
> >   1.8e+06
> >++----------------------------------------------------------------+
> >
> >
> >                                   turbostat.Pkg_W
> >
> >    ++--------------------------------------------------------------------+
> >    O+ O   O     O      O                O                                |
> >    |         O      O     O   O  O  O      O      O     O   O  O  O      |
> >    ++                                         O      O                   |
> >    ++                                                                    |
> >    ++                                                                    |
> >    ++                                                                    |
> >    |                                                                     |
> >    ++                                                                    |
> >    ++                                                                    |
> >    ++        *..      .*..                                               |
> >    *+.*... ..   *...*.    *...*..*..*...*..*..  ..*..   *...*..*..*...*..*
> >    |      *                                   *.      ..                 |
> >    ++                                                *                   |
> >    ++--------------------------------------------------------------------+
> >
> >
> >                                   turbostat.Cor_W
> >
> >    ++--------------------------------------------------------------------+
> >    O+ O   O  O  O   O  O                O  O                      O      |
> >    |                      O   O  O  O         O   O  O  O   O  O         |
> >    ++                                                                    |
> >    ++                                                                    |
> >    |                                                                     |
> >    ++                                                                    |
> >    ++                                                                    |
> >    ++                                                                    |
> >    |                                                                     |
> >    ++        *..                                                         |
> >    *+.*... ..   *...*..*..*...*..*..*...*..*..  ..*..   *...  .*..*...*..*
> >    |      *                                   *.      ..    *.           |
> >    ++                                                *                   |
> >    ++--------------------------------------------------------------------+
> >
> >
> >                                  turbostat.RAM_W
> >
> >   ++---------------------------------------------------------------------+
> >   |  O      O         O                O   O         O         O  O      |
> >   O+     O         O      O  O  O   O         O  O      O  O             |
> >   |             O                                                        |
> >   ++                                                                     |
> >   |                                                                      |
> >   ++                                                                     |
> >   |                                                                      |
> >   ++                                                                     |
> >   |                   *                                                  |
> >   ++                .. +                      *..                        |
> >   |            .*..*    +    *..       *..   +     ..*..*..      .*...   |
> >   ++         ..          + ..        ..   . +    *.        *...*.     *..*
> >   *..*...*..*             *     *...*      *                             |
> >   ++---------------------------------------------------------------------+
> >
> >
> >     [*] bisect-good sample
> >     [O] bisect-bad  sample
> >
> >
> >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,
> >Jet
> >
> >
> 
> -- 
> Yoshihiro YUNOMAE
> Software Platform Research Dept. Linux Technology Center
> Hitachi, Ltd., Yokohama Research Laboratory
> E-mail: yoshihiro.yunomae.ez@...achi.com
> 
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