LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Aaron Lu <aaron.lu@intel.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: "Ye, Xiaolong" <xiaolong.ye@intel.com>,
	"tj@kernel.org" <tj@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"lkp@01.org" <lkp@01.org>,
	"hannes@cmpxchg.org" <hannes@cmpxchg.org>
Subject: Re: [LKP] [lkp-robot] [mm, memcontrol] 309fe96bfc: vm-scalability.throughput +23.0% improvement
Date: Tue, 29 May 2018 17:00:24 +0800	[thread overview]
Message-ID: <20180529090024.GC14785@intel.com> (raw)
In-Reply-To: <20180529082751.GQ27180@dhcp22.suse.cz>

On Tue, May 29, 2018 at 10:27:51AM +0200, Michal Hocko wrote:
> On Tue 29-05-18 16:11:27, Aaron Lu wrote:
> > On Tue, May 29, 2018 at 09:58:00AM +0200, Michal Hocko wrote:
> > > On Tue 29-05-18 03:15:51, Lu, Aaron wrote:
> > > > On Mon, 2018-05-28 at 14:03 +0200, Michal Hocko wrote:
> > > > > On Mon 28-05-18 19:40:19, kernel test robot wrote:
> > > > > > 
> > > > > > Greeting,
> > > > > > 
> > > > > > FYI, we noticed a +23.0% improvement of vm-scalability.throughput due to commit:
> > > > > > 
> > > > > > 
> > > > > > commit: 309fe96bfc0ae387f53612927a8f0dc3eb056efd ("mm, memcontrol: implement memory.swap.events")
> > > > > > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
> > > > > 
> > > > > This doesn't make any sense to me. The patch merely adds an accounting.
> > > > > It doesn't optimize anything. So I strongly suspect the result is just
> > > > > misleading or the test (environment) misconfigured. Not the first time
> > > > > I am seeing something like that I am afraid.
> > > > > 
> > > > 
> > > > Most likely the same situation as:
> > > > "
> > > > FYI, we noticed a -27.2% regression of will-it-scale.per_process_ops
> > > > due to commit:
> > > > 
> > > > 
> > > > commit: e27be240df53f1a20c659168e722b5d9f16cc7f4 ("mm: memcg: make sure
> > > > memory.events is uptodate when waking pollers")
> > > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> > > > "
> > > > 
> > > > Where the performance change is due to layout change of
> > > > 'struct mem_cgroup':
> > > > http://lkml.kernel.org/r/20180528085201.GA2918@intel.com
> > > 
> > > I do not follow. How can _this_ patch lead to an improvement when it
> > > actually _adds_ an accounting? The other report you are mentioning is a
> > 
> > This patch also changed the layout of 'struct mem_cgroup':
> > 
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index d99b71bc2c66..517096c3cc99 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -208,6 +210,9 @@ struct mem_cgroup {
> >  	atomic_long_t memory_events[MEMCG_NR_MEMORY_EVENTS];
> >  	struct cgroup_file events_file;
> >  
> > +	/* handle for "memory.swap.events" */
> > +	struct cgroup_file swap_events_file;
> > +
> >  	/* protect arrays of thresholds */
> >  	struct mutex thresholds_lock;
> > 
> > And I'm guessing that might be the cause.
> 
> Ohh, you are right! Sorry, I've missed that part.

Never mind, I want to thank you for taking a look at these reports :-)

I just tried to move this newly added field to the bottom of the
structure(just above 'struct mem_cgroup_per_node *nodeinfo[0];'), and
performance dropped to 82665166, still much better than base but already
worse than this patch.

As you said in another email, this is really fragile.

  reply	other threads:[~2018-05-29  9:00 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-28 11:40 kernel test robot
2018-05-28 12:03 ` Michal Hocko
2018-05-29  3:15   ` [LKP] " Lu, Aaron
2018-05-29  7:58     ` Michal Hocko
2018-05-29  8:11       ` Aaron Lu
2018-05-29  8:27         ` Michal Hocko
2018-05-29  9:00           ` Aaron Lu [this message]
2018-06-01  7:26 ` Aaron Lu
2018-06-06  8:50   ` Aaron Lu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180529090024.GC14785@intel.com \
    --to=aaron.lu@intel.com \
    --cc=hannes@cmpxchg.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=lkp@01.org \
    --cc=mhocko@kernel.org \
    --cc=tj@kernel.org \
    --cc=xiaolong.ye@intel.com \
    --subject='Re: [LKP] [lkp-robot] [mm, memcontrol] 309fe96bfc: vm-scalability.throughput +23.0% improvement' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).