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 <[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 */
Best Regards,
Rong Chen
