linux-kernel - Re: [LKP] [lkp] [futex] 65d8fc777f: +25.6% will-it-scale.per_process

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Date:	Mon, 21 Mar 2016 16:42:47 +0800
From:	"Huang\, Ying" <ying.huang@...el.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	"Huang\, Ying" <ying.huang@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Chris Mason <clm@...com>,
	Peter Zijlstra <peterz@...radead.org>, <lkp@...org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	"Davidlohr Bueso" <dbueso@...e.de>,
	Hugh Dickins <hughd@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Darren Hart <dvhart@...ux.intel.com>,
	"Wu Fengguang" <fengguang.wu@...el.com>,
	Xiaolong Ye <xiaolong.ye@...el.com>
Subject: Re: [LKP] [lkp] [futex] 65d8fc777f: +25.6% will-it-scale.per_process_ops

Thomas Gleixner <tglx@...utronix.de> writes:

> On Mon, 21 Mar 2016, Huang, Ying wrote:
>> >  FYI, we noticed 25.6% performance improvement due to commit
>> >
>> >    65d8fc777f6d "futex: Remove requirement for lock_page() in get_futex_key()"
>> >
>> >  in the will-it-scale.per_process_ops test.
>> >
>> >  will-it-scale.per_process_ops tests the futex operations for process shared
>> >  futexes (Or whatever that test really does).
>> 
>> There is a futex sub test case for will-it-scale test suite.  But I got your
>> point, we need some description for the test case.  If email is not too
>> limited for the full description, we will put it in some web site and
>> include short description and link to the full description in email.
>
> Ok. Just make sure the short description gives enough information for the
> casual reader.
>  
>> >  The commit has no significant impact on any other test in the test suite.
>> 
>> Sorry, we have no enough machine power to test all test cases for each
>> bisect result.  So we will have no such information until we find a way
>> to do that.
>
> Well, then I really have to ask how I should interpret the data here:
>
>    5076304 ±  0%     +25.6%    6374220 ±  0%  will-it-scale.per_process_ops
>
>    ^^^ That's the reason why you sent the mail in the first place
>
>    1194117 ±  0%     +14.4%    1366153 ±  1%  will-it-scale.per_thread_ops
>       0.58 ±  0%      -2.0%       0.57 ±  0%  will-it-scale.scalability
>       6820 ±  0%     -19.6%       5483 ± 15%  meminfo.AnonHugePages
>       2652 ±  5%     -10.4%       2375 ±  2%  vmstat.system.cs
>       2848 ± 32%    +141.2%       6870 ± 65%  numa-meminfo.node1.Active(anon)
>       2832 ± 31%     +57.6%       4465 ± 27%  numa-meminfo.node1.AnonPages
>      15018 ± 12%     -23.3%      11515 ± 15%  numa-meminfo.node2.AnonPages
>       1214 ± 14%     -22.8%     936.75 ± 20%  numa-meminfo.node3.PageTables
>     712.25 ± 32%    +141.2%       1718 ± 65%  numa-vmstat.node1.nr_active_anon
>     708.25 ± 31%     +57.7%       1116 ± 27%  numa-vmstat.node1.nr_anon_pages
>
> How is this related and what should I do about this information? 

For each will-it-scale sub test case, it will be run in both process
mode and thread mode, and task number will change from 1 to CPU number.
will-it-scale.per_thread_ops shows thread mode main result.
will-it-scale.scalability is calculated to measure how per_process_ops
and per_thread_ops scaled along with the task number.  These are default
behavior of will-it-scale test suite.

Others are monitors output.  That is, other information collected during
test.  For example, meminfo is a monitor to sampling /proc/meminfo
contents,  AnonHugePages is a line in it.  meminfo.AnonHugePages is for
the average value of AnonHugePages line of /proc/meminfo.  Similarly
vmstat.system.cs is the average value of cs column of system column
group of /usr/bin/vmstat.

We hope these information are helpful for root causing the regression.

>  If it's important then I have to admit, that I fail to understand why.
>
>  If it's not important then I have to ask why is this included.
>
>> > So that allows me to reproduce that test more or less with no effort. And
>> > that's the really important part.
>> 
>> For reproducing, now we use lkp-tests tool, which includes scripts to
>> build the test case, run the test, collect various information, compare
>> the test result, with the job file attached with the report email.  That
>> is not the easiest way, we will continuously improve it.
>
> I know and lkp-tests is a pain to work with. So please look into a way to
> extract the relevant binaries, so it's simple for developers to reproduce.

OK.  We will try to improve on this side.  But it is not an easy task
for us to provided easy to use simple binaries.  Do you think something
like Docker image is easy to use?

>> > You can provide nice charts and full comparison tables for all tests on a web
>> > site for those who are interested in large stats and pretty charts.
>> >
>> > Full results: http://wherever.you.store/your/results/test-nr/results
>> 
>> Before we have a website for detailed information, we will still put
>> some details into report email.
>
> Ok, but please make them understandable for mere mortals.

Sure.

Best Regards,
Huang, Ying

> Thanks,
>
> 	tglx