From: Feng Tang <feng.tang@intel.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>,
Waiman Long <longman@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Shakeel Butt <shakeelb@google.com>,
Chris Down <chris@chrisdown.name>,
Johannes Weiner <hannes@cmpxchg.org>,
Roman Gushchin <guro@fb.com>, Tejun Heo <tj@kernel.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Yafang Shao <laoar.shao@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
lkp@lists.01.org, lkp@intel.com, zhengjun.xing@intel.com,
ying.huang@intel.com
Subject: Re: [LKP] Re: [mm/memcg] bd0b230fe1: will-it-scale.per_process_ops -22.7% regression
Date: Thu, 12 Nov 2020 20:28:44 +0800 [thread overview]
Message-ID: <20201112122844.GA11000@shbuild999.sh.intel.com> (raw)
In-Reply-To: <20201104081546.GB10052@dhcp22.suse.cz>
Hi Michal,
On Wed, Nov 04, 2020 at 09:15:46AM +0100, Michal Hocko wrote:
> > > > Hi Michal,
> > > >
> > > > We used the default configure of cgroups, not sure what configuration you
> > > > want,
> > > > could you give me more details? and here is the cgroup info of will-it-scale
> > > > process:
> > > >
> > > > $ cat /proc/3042/cgroup
> > > > 12:hugetlb:/
> > > > 11:memory:/system.slice/lkp-bootstrap.service
> > >
> > > OK, this means that memory controler is enabled and in use. Btw. do you
> > > get the original performance if you add one phony page_counter after the
> > > union?
> > >
> > I add one phony page_counter after the union and re-test, the regression
> > reduced to -1.2%. It looks like the regression caused by the data structure
> > layout change.
>
> Thanks for double checking. Could you try to cache align the
> page_counter struct? If that helps then we should figure which counters
> acks against each other by adding the alignement between the respective
> counters.
We tried below patch to make the 'page_counter' aligned.
diff --git a/include/linux/page_counter.h b/include/linux/page_counter.h
index bab7e57..9efa6f7 100644
--- a/include/linux/page_counter.h
+++ b/include/linux/page_counter.h
@@ -26,7 +26,7 @@ struct page_counter {
/* legacy */
unsigned long watermark;
unsigned long failcnt;
-};
+} ____cacheline_internodealigned_in_smp;
and with it, the -22.7% peformance change turns to a small -1.7%, which
confirms the performance bump is caused by the change to data alignment.
After the patch, size of 'page_counter' increases from 104 bytes to 128
bytes, and the size of 'mem_cgroup' increases from 2880 bytes to 3008
bytes(with our kernel config). Another major data structure which
contains 'page_counter' is 'hugetlb_cgroup', whose size will change
from 912B to 1024B.
Should we make these page_counters aligned to reduce cacheline conflict?
Thanks,
Feng
next prev parent reply other threads:[~2020-11-12 12:28 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-02 9:15 [mm/memcg] bd0b230fe1: will-it-scale.per_process_ops -22.7% regression kernel test robot
2020-11-02 9:27 ` Michal Hocko
2020-11-02 9:53 ` [LKP] " Rong Chen
2020-11-02 10:02 ` Michal Hocko
2020-11-04 1:20 ` Xing Zhengjun
2020-11-04 2:46 ` Waiman Long
2020-11-04 8:15 ` Michal Hocko
2020-11-12 12:28 ` Feng Tang [this message]
2020-11-12 14:16 ` Michal Hocko
2020-11-12 16:43 ` Waiman Long
2020-11-13 7:39 ` Feng Tang
2020-11-13 7:34 ` Feng Tang
2020-11-20 11:44 ` Feng Tang
2020-11-20 13:19 ` Michal Hocko
2020-11-20 14:30 ` Feng Tang
2020-11-25 6:24 ` Feng Tang
2020-11-26 1:34 ` Waiman Long
2020-11-26 17:39 ` Linus Torvalds
2020-11-30 8:48 ` Michal Hocko
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