Messages in this thread | | | Date | Thu, 21 Feb 2019 08:10:23 +0100 | From | Greg Kroah-Hartman <> | 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 > > > 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 */
While this is fun to worry about alignment and structure size of 'struct device' I find it odd given that the syscalls and userspace load of those test programs have nothing to do with 'struct device' at all.
So I can work on fixing up the alignment of struct device, as that's a nice thing to do for systems with 30k of these in memory, but that shouldn't affect a workload of a constant string of signal calls.
thanks,
greg k-h
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