linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Dan Williams <dan.j.williams@intel.com>
To: Jan Kara <jack@suse.cz>
Cc: "John Hubbard" <jhubbard@nvidia.com>,
	"kernel test robot" <oliver.sang@intel.com>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	"Ira Weiny" <ira.weiny@intel.com>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Dave Chinner" <david@fromorbit.com>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Michal Hocko" <mhocko@suse.com>,
	"Mike Kravetz" <mike.kravetz@oracle.com>,
	"Shuah Khan" <shuah@kernel.org>,
	"Vlastimil Babka" <vbabka@suse.cz>,
	LKML <linux-kernel@vger.kernel.org>,
	lkp@lists.01.org, "kbuild test robot" <lkp@intel.com>,
	"Huang, Ying" <ying.huang@intel.com>,
	"feng tang" <feng.tang@intel.com>,
	"Zhengjun Xing" <zhengjun.xing@intel.com>,
	guobing.chen@intel.com, ming.a.chen@intel.com,
	frank.du@intel.com, Shuhua.Fan@intel.com, wangyang.guo@intel.com,
	Wenhuan.Huang@intel.com, jessica.ji@intel.com,
	shan.kang@intel.com, guangli.li@intel.com, tiejun.li@intel.com,
	yu.ma@intel.com, dapeng1.mi@intel.com, jiebin.sun@intel.com,
	gengxin.xie@intel.com, fan.zhao@intel.com
Subject: Re: [mm/gup] 47e29d32af: phoronix-test-suite.npb.FT.A.total_mop_s -45.0% regression
Date: Wed, 18 Nov 2020 10:17:27 -0800	[thread overview]
Message-ID: <CAPcyv4g=MFAojCeCST+sF22A+2cetVMFmQuDtu7arEM+0a+Ebw@mail.gmail.com> (raw)
In-Reply-To: <20201118134952.GE1981@quack2.suse.cz>

On Wed, Nov 18, 2020 at 5:51 AM Jan Kara <jack@suse.cz> wrote:
>
> On Mon 16-11-20 19:35:31, John Hubbard wrote:
> >
> > On 11/16/20 6:48 PM, kernel test robot wrote:
> > >
> > > Greeting,
> > >
> > > FYI, we noticed a -45.0% regression of phoronix-test-suite.npb.FT.A.total_mop_s due to commit:
> > >
> >
> > That's a huge slowdown...
> >
> > >
> > > commit: 47e29d32afba11b13efb51f03154a8cf22fb4360 ("mm/gup: page->hpage_pinned_refcount: exact pin counts for huge pages")
> > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> >
> > ...but that commit happened in April, 2020. Surely if this were a serious
> > issue we would have some other indication...is this worth following up
> > on?? I'm inclined to ignore it, honestly.
>
> Why this was detected so late is a fair question although it doesn't quite
> invalidate the report...

I don't know what specifically happened in this case, perhaps someone
from the lkp team can comment? However, the myth / contention that
"surely someone else would have noticed by now" is why the lkp project
was launched. Kernels regressed without much complaint and it wasn't
until much later in the process, around the time enterprise distros
rebased to new kernels, did end users start filing performance loss
regression reports. Given -stable kernel releases, 6-7 months is still
faster than many end user upgrade cycles to new kernel baselines.

  reply	other threads:[~2020-11-18 18:17 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-17  2:48 [mm/gup] 47e29d32af: phoronix-test-suite.npb.FT.A.total_mop_s -45.0% regression kernel test robot
2020-11-17  3:35 ` John Hubbard
2020-11-18 13:49   ` Jan Kara
2020-11-18 18:17     ` Dan Williams [this message]
2020-11-18 19:32       ` John Hubbard
2020-11-20  2:42       ` Oliver Sang

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='CAPcyv4g=MFAojCeCST+sF22A+2cetVMFmQuDtu7arEM+0a+Ebw@mail.gmail.com' \
    --to=dan.j.williams@intel.com \
    --cc=Shuhua.Fan@intel.com \
    --cc=Wenhuan.Huang@intel.com \
    --cc=akpm@linux-foundation.org \
    --cc=corbet@lwn.net \
    --cc=dapeng1.mi@intel.com \
    --cc=david@fromorbit.com \
    --cc=fan.zhao@intel.com \
    --cc=feng.tang@intel.com \
    --cc=frank.du@intel.com \
    --cc=gengxin.xie@intel.com \
    --cc=guangli.li@intel.com \
    --cc=guobing.chen@intel.com \
    --cc=hch@infradead.org \
    --cc=ira.weiny@intel.com \
    --cc=jack@suse.cz \
    --cc=jessica.ji@intel.com \
    --cc=jgg@ziepe.ca \
    --cc=jglisse@redhat.com \
    --cc=jhubbard@nvidia.com \
    --cc=jiebin.sun@intel.com \
    --cc=kirill.shutemov@linux.intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=lkp@intel.com \
    --cc=lkp@lists.01.org \
    --cc=mhocko@suse.com \
    --cc=mike.kravetz@oracle.com \
    --cc=ming.a.chen@intel.com \
    --cc=oliver.sang@intel.com \
    --cc=shan.kang@intel.com \
    --cc=shuah@kernel.org \
    --cc=tiejun.li@intel.com \
    --cc=torvalds@linux-foundation.org \
    --cc=vbabka@suse.cz \
    --cc=viro@zeniv.linux.org.uk \
    --cc=wangyang.guo@intel.com \
    --cc=willy@infradead.org \
    --cc=ying.huang@intel.com \
    --cc=yu.ma@intel.com \
    --cc=zhengjun.xing@intel.com \
    /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
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
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).