Re: [tracing] 939c7a4f04f: -46.4% cpuidle.C3-IVT.time

From: Fengguang Wu
Date: Thu Jun 19 2014 - 12:28:53 EST

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@xxxxxxxxxxx
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/