Wei Yang <[email protected]> writes: > 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 <[email protected]> >>Date: Wed Feb 20 14:21:19 2019 +0800 >> >> backfile klist_node in struct device for debugging >> >> Signed-off-by: 0day robot <[email protected]> >> >>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.
I guess because the size of struct device is changed, it influences some alignment changes in the system. Thus influence the benchmark score. Best Regards, Huang, Ying >> >>Best Regards, >>Rong Chen
