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Date: Thu, 21 Feb 2019 11:46:12 +0800
From: Wei Yang <richardw.yang@...ux.intel.com>
To: kernel test robot <rong.a.chen@...el.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
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 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@...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 */
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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