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Date:   Thu, 21 Feb 2019 13:46:54 +0800
From:   kernel test robot <rong.a.chen@intel.com>
To:     Wei Yang <richardw.yang@linux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>, lkp@01.org,
        "Huang, Ying" <ying.huang@intel.com>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [LKP] [driver core] 570d020012: will-it-scale.per_thread_ops
 -12.2% regression
Message-ID: <20190221054654.GC28147@shao2-debian>
References: <20190218075442.GI29177@shao2-debian>
 <20190219005945.GA16734@richard>
 <20190219121904.GA24103@kroah.com>
 <20190221031049.GE28258@shao2-debian>
 <20190221034612.GA15147@richard>
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In-Reply-To: <20190221034612.GA15147@richard>
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On Thu, Feb 21, 2019 at 11:46:12AM +0800, Wei Yang wrote:
> On Thu, Feb 21, 2019 at 11:10:49AM +0800, kernel test robot wrote:
> >On Tue, Feb 19, 2019 at 01:19:04PM +0100, Greg Kroah-Hartman wrote:
> >> On Tue, Feb 19, 2019 at 08:59:45AM +0800, Wei Yang wrote:
> >> > On Mon, Feb 18, 2019 at 03:54:42PM +0800, kernel test robot wrote:
> >> > >Greeting,
> >> > >
> >> > >FYI, we noticed a -12.2% regression of will-it-scale.per_thread_ops due to commit:
> >> > >
> >> > >
> >> > >commit: 570d0200123fb4f809aa2f6226e93a458d664d70 ("driver core: move device->knode_class to device_private")
> >> > >https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
> >> > >
> >> > 
> >> > This is interesting.
> >> > 
> >> > I didn't expect the move of this field will impact the performance.
> >> > 
> >> > The reason is struct device is a hotter memory than device->device_private?
> >> > 
> >> > >in testcase: will-it-scale
> >> > >on test machine: 288 threads Knights Mill with 80G memory
> >> > >with following parameters:
> >> > >
> >> > >	nr_task: 100%
> >> > >	mode: thread
> >> > >	test: unlink2
> >> > >	cpufreq_governor: performance
> >> > >
> >> > >test-description: Will It Scale takes a testcase and runs it from 1 through to n parallel copies to see if the testcase will scale. It builds both a process and threads based test in order to see any differences between the two.
> >> > >test-url: https://github.com/antonblanchard/will-it-scale
> >> > >
> >> > >In addition to that, the commit also has significant impact on the following tests:
> >> > >
> >> > >+------------------+---------------------------------------------------------------+
> >> > >| testcase: change | will-it-scale: will-it-scale.per_thread_ops -29.9% regression |
> >> > >| test machine     | 288 threads Knights Mill with 80G memory                      |
> >> > >| test parameters  | cpufreq_governor=performance                                  |
> >> > >|                  | mode=thread                                                   |
> >> > >|                  | nr_task=100%                                                  |
> >> > >|                  | test=signal1                                                  |
> >> 
> >> Ok, I'm going to blame your testing system, or something here, and not
> >> the above patch.
> >> 
> >> All this test does is call raise(3).  That does not touch the driver
> >> core at all.
> >> 
> >> > >+------------------+---------------------------------------------------------------+
> >> > >| testcase: change | will-it-scale: will-it-scale.per_thread_ops -16.5% regression |
> >> > >| test machine     | 288 threads Knights Mill with 80G memory                      |
> >> > >| test parameters  | cpufreq_governor=performance                                  |
> >> > >|                  | mode=thread                                                   |
> >> > >|                  | nr_task=100%                                                  |
> >> > >|                  | test=open1                                                    |
> >> > >+------------------+---------------------------------------------------------------+
> >> 
> >> Same here, open1 just calls open/close a lot.  No driver core
> >> interaction at all there either.
> >> 
> >> So are you _sure_ this is the offending patch?
> >
> >Hi Greg,
> >
> >We did an experiment, recovered the layout of struct device. and we
> >found the regression is gone. I guess the regession is not from the
> >patch but related to the struct layout.
> >
> >
> >tests: 1
> >testcase/path_params/tbox_group/run: will-it-scale/performance-thread-100%-unlink2/lkp-knm01
> >
> >570d0200123fb4f8  a36dc70b810afe9183de2ea18f  
> >----------------  --------------------------  
> >         %stddev      change         %stddev
> >             \          |                \  
> >    237096              14%     270789        will-it-scale.workload
> >       823              14%        939        will-it-scale.per_thread_ops
> >
> 
> Do you have the comparison between a36dc70b810afe9183de2ea18f and the one
> before 570d020012?

testcase/path_params/tbox_group/run: will-it-scale/performance-thread-100%-unlink2/lkp-knm01

4bd4e92cfe6d2af7 a36dc70b810afe9183de2ea18f 
---------------- -------------------------- 
         %stddev     %change         %stddev
             \          |                \  
    937.00            +0.2%     939.33        will-it-scale.per_thread_ops
    269989            +0.3%     270789        will-it-scale.workload

> >
> >tests: 1
> >testcase/path_params/tbox_group/run: will-it-scale/performance-thread-100%-signal1/lkp-knm01
> >
> >570d0200123fb4f8  a36dc70b810afe9183de2ea18f  
> >----------------  --------------------------  
> >         %stddev      change         %stddev
> >             \          |                \  
> >     93.51 ±  3%        48%     138.53 ±  3%  will-it-scale.time.user_time
> >       186              40%        261        will-it-scale.per_thread_ops
> >     53909              40%      75507        will-it-scale.workload
> >

testcase/path_params/tbox_group/run: will-it-scale/performance-thread-100%-signal1/lkp-knm01

4bd4e92cfe6d2af7 a36dc70b810afe9183de2ea18f 
---------------- -------------------------- 
         %stddev     %change         %stddev
             \          |                \  
    266.00 ±  2%      -1.6%     261.67        will-it-scale.per_thread_ops
     76699 ±  2%      -1.6%      75507        will-it-scale.workload

> >
> >tests: 1
> >testcase/path_params/tbox_group/run: will-it-scale/performance-thread-100%-open1/lkp-knm01
> >
> >570d0200123fb4f8  a36dc70b810afe9183de2ea18f  
> >----------------  --------------------------  
> >         %stddev      change         %stddev
> >             \          |                \  
> >    447722              22%     546258 ± 10%  will-it-scale.time.involuntary_context_switches
> >    226995              19%     269751        will-it-scale.workload
> >       787              19%        936        will-it-scale.per_thread_ops
> >
> >

testcase/path_params/tbox_group/run: will-it-scale/performance-thread-100%-open1/lkp-knm01

4bd4e92cfe6d2af7 a36dc70b810afe9183de2ea18f 
---------------- -------------------------- 
         %stddev     %change         %stddev
             \          |                \  
    944.60            -0.9%     936.00        will-it-scale.per_thread_ops
    272252            -0.9%     269751        will-it-scale.workload

Best Regards,
Rong Chen