Messages in this thread | | | Date | Thu, 21 Feb 2019 11:46:12 +0800 | From | Wei Yang <> | Subject | Re: [LKP] [driver core] 570d020012: will-it-scale.per_thread_ops -12.2% regression |
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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?
> >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@intel.com> >Date: Wed Feb 20 14:21:19 2019 +0800 > > backfile klist_node in struct device for debugging > > Signed-off-by: 0day robot <lkp@intel.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 */
Hmm... because this is not properly aligned?
struct klist_node { void *n_klist; /* never access directly */ struct list_head n_node; struct kref n_ref; };
Except struct kref has one "int" type, others are pointers.
But... I am still confused.
> >Best Regards, >Rong Chen
-- Wei Yang Help you, Help me
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