LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Andrea Arcangeli <aarcange@redhat.com>
To: David Rientjes <rientjes@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	mgorman@techsingularity.net, Vlastimil Babka <vbabka@suse.cz>,
	mhocko@kernel.org, ying.huang@intel.com, s.priebe@profihost.ag,
	Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
	alex.williamson@redhat.com, lkp@01.org, kirill@shutemov.name,
	Andrew Morton <akpm@linux-foundation.org>,
	zi.yan@cs.rutgers.edu
Subject: Re: [LKP] [mm] ac5b2c1891: vm-scalability.throughput -61.3% regression
Date: Wed, 5 Dec 2018 19:54:25 -0500
Message-ID: <20181206005425.GB21159@redhat.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1812051614410.50028@chino.kir.corp.google.com>

On Wed, Dec 05, 2018 at 04:18:14PM -0800, David Rientjes wrote:
> On Wed, 5 Dec 2018, Andrea Arcangeli wrote:
> 
> > __GFP_COMPACT_ONLY gave an hope it could give some middle ground but
> > it shows awful compaction results, it basically destroys compaction
> > effectiveness and we know why (COMPACT_SKIPPED must call reclaim or
> > compaction can't succeed because there's not enough free memory in the
> > node). If somebody used MADV_HUGEPAGE compaction should still work and
> > not fail like that. Compaction would fail to be effective even in the
> > local node where __GFP_THISNODE didn't fail. Worst of all it'd fail
> > even on non-NUMA systems (that would be easy to fix though by making
> > the HPAGE_PMD_ORDER check conditional to NUMA being enabled at
> > runtime).
> > 
> 
> Note that in addition to COMPACT_SKIPPED that you mention, compaction can 
> fail with COMPACT_COMPLETE, meaning the full scan has finished without 
> freeing a hugepage, or COMPACT_DEFERRED, meaning that doing another scan 
> is unlikely to produce a different result.  COMPACT_SKIPPED makes sense to 
> do reclaim if it can become accessible to isolate_freepages() and 
> hopefully another allocator does not allocate from these newly freed pages 
> before compaction can scan the zone again.  For COMPACT_COMPLETE and 
> COMPACT_DEFERRED, reclaim is unlikely to ever help.

The COMPACT_COMPLETE and (COMPACT_PARTIAL_SKIPPED for that matter)
seems just a mistake in the max() evaluation try_to_compact_pages()
that let it return COMPACT_COMPLETE and COMPACT_PARTIAL_SKIPPED. I
think it should just return COMPACT_DEFERRED in those two cases and it
should be enforced forced for all prio.

There are really only 3 cases that matter for the caller:

1) succeed -> we got the page
2) defer -> we failed (caller won't care about why)
3) skipped -> failed because not enough 4k freed -> reclaim must be invoked then
   compaction can be retried

PARTIAL_SKIPPED/COMPLETE both fall into 2) above so for the caller
they should be treated the same way. It doesn't seem very concerning
that it may try like if it succeeded and do a spurious single reclaim
invocation, but it's good to fix this and take the COMPACT_DEFERRED
nopage path in the __GFP_NORETRY case.

  reply index

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-27  6:25 kernel test robot
2018-11-27 17:08 ` Linus Torvalds
2018-11-27 18:17   ` Michal Hocko
2018-11-27 18:21     ` Michal Hocko
2018-11-27 19:05   ` Vlastimil Babka
2018-11-27 19:16     ` Vlastimil Babka
2018-11-27 20:57   ` Andrea Arcangeli
2018-11-27 22:50     ` Linus Torvalds
2018-11-28  6:30       ` Michal Hocko
2018-11-28  3:20     ` Huang\, Ying
2018-11-28 16:48       ` Linus Torvalds
2018-11-28 18:39         ` Andrea Arcangeli
2018-11-28 23:10         ` David Rientjes
2018-12-03 18:01         ` Linus Torvalds
2018-12-03 18:14           ` Michal Hocko
2018-12-03 18:19             ` Linus Torvalds
2018-12-03 18:30               ` Michal Hocko
2018-12-03 18:45                 ` Linus Torvalds
2018-12-03 18:59                   ` Michal Hocko
2018-12-03 19:23                     ` Andrea Arcangeli
2018-12-03 20:26                       ` David Rientjes
2018-12-03 19:28                     ` Linus Torvalds
2018-12-03 20:12                       ` Andrea Arcangeli
2018-12-03 20:36                         ` David Rientjes
2018-12-03 22:04                         ` Linus Torvalds
2018-12-03 22:27                           ` Linus Torvalds
2018-12-03 22:57                             ` David Rientjes
2018-12-04  9:22                             ` Vlastimil Babka
2018-12-04 10:45                               ` Mel Gorman
2018-12-05  0:47                                 ` David Rientjes
2018-12-05  9:08                                   ` Michal Hocko
2018-12-05 10:43                                     ` Mel Gorman
2018-12-05 11:43                                       ` Michal Hocko
2018-12-05 10:06                                 ` Mel Gorman
2018-12-05 20:40                                 ` Andrea Arcangeli
2018-12-05 21:59                                   ` David Rientjes
2018-12-06  0:00                                     ` Andrea Arcangeli
2018-12-05 22:03                                   ` Linus Torvalds
2018-12-05 22:12                                     ` David Rientjes
2018-12-05 23:36                                     ` Andrea Arcangeli
2018-12-05 23:51                                       ` Linus Torvalds
2018-12-06  0:58                                         ` Linus Torvalds
2018-12-06  9:14                                           ` MADV_HUGEPAGE vs. NUMA semantic (was: Re: [LKP] [mm] ac5b2c1891: vm-scalability.throughput -61.3% regression) Michal Hocko
2018-12-06 23:49                                             ` David Rientjes
2018-12-07  7:34                                               ` Michal Hocko
2018-12-07  4:31                                             ` Linus Torvalds
2018-12-07  7:49                                               ` Michal Hocko
2018-12-07  9:06                                                 ` Vlastimil Babka
2018-12-07 23:15                                                   ` David Rientjes
2018-12-06 23:43                                           ` [LKP] [mm] ac5b2c1891: vm-scalability.throughput -61.3% regression David Rientjes
2018-12-07  4:01                                             ` Linus Torvalds
2018-12-10  0:29                                               ` David Rientjes
2018-12-10  4:49                                                 ` Andrea Arcangeli
2018-12-12  0:37                                                   ` David Rientjes
2018-12-12  9:50                                                     ` Michal Hocko
2018-12-12 17:00                                                       ` Andrea Arcangeli
2018-12-14 11:32                                                         ` Michal Hocko
2018-12-12 10:14                                                     ` Vlastimil Babka
2018-12-14 21:04                                                       ` David Rientjes
2018-12-14 21:33                                                         ` Vlastimil Babka
2018-12-21 22:18                                                           ` David Rientjes
2018-12-22 12:08                                                             ` Mel Gorman
2018-12-14 23:11                                                         ` Mel Gorman
2018-12-21 22:15                                                           ` David Rientjes
2018-12-12 10:44                                                   ` Andrea Arcangeli
2019-04-15 11:48                                             ` Michal Hocko
2018-12-06  0:18                                       ` David Rientjes
2018-12-06  0:54                                         ` Andrea Arcangeli [this message]
2018-12-06  9:23                                           ` Vlastimil Babka
2018-12-03 20:39                     ` David Rientjes
2018-12-03 21:25                       ` Michal Hocko
2018-12-03 21:53                         ` David Rientjes
2018-12-04  8:48                           ` Michal Hocko
2018-12-05  0:07                             ` David Rientjes
2018-12-05 10:18                               ` Michal Hocko
2018-12-05 19:16                                 ` David Rientjes
2018-11-27  7:23 kernel test robot

Reply instructions:

You may reply publically 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=20181206005425.GB21159@redhat.com \
    --to=aarcange@redhat.com \
    --cc=akpm@linux-foundation.org \
    --cc=alex.williamson@redhat.com \
    --cc=kirill@shutemov.name \
    --cc=linux-kernel@vger.kernel.org \
    --cc=lkp@01.org \
    --cc=mgorman@techsingularity.net \
    --cc=mhocko@kernel.org \
    --cc=rientjes@google.com \
    --cc=s.priebe@profihost.ag \
    --cc=torvalds@linux-foundation.org \
    --cc=vbabka@suse.cz \
    --cc=ying.huang@intel.com \
    --cc=zi.yan@cs.rutgers.edu \
    /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

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org linux-kernel@archiver.kernel.org
	public-inbox-index lkml


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/ public-inbox