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Date: Thu, 21 Feb 2019 11:10:49 +0800 From: kernel test robot <rong.a.chen@...el.com> To: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Cc: Wei Yang <richardw.yang@...ux.intel.com>, Stephen Rothwell <sfr@...b.auug.org.au>, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, lkp@...org, "Huang, Ying" <ying.huang@...el.com>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [LKP] [driver core] 570d020012: will-it-scale.per_thread_ops -12.2% regression 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 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 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 commit a36dc70b810afe9183de2ea18faa4c0939c139ac Author: 0day robot <lkp@...el.com> Date: Wed Feb 20 14:21:19 2019 +0800 backfile klist_node in struct device for debugging Signed-off-by: 0day robot <lkp@...el.com> diff --git a/include/linux/device.h b/include/linux/device.h index d0e452fd0bff2..31666cb72b3ba 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -1035,6 +1035,7 @@ struct device { spinlock_t devres_lock; struct list_head devres_head; + struct klist_node knode_class_test_by_rongc; struct class *class; const struct attribute_group **groups; /* optional groups */ Best Regards, Rong Chen
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