LKML Archive on lore.kernel.org
 help / color / Atom feed
From: David Rientjes <rientjes@google.com>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	ying.huang@intel.com, s.priebe@profihost.ag,
	mgorman@techsingularity.net,
	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, Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [LKP] [mm] ac5b2c1891: vm-scalability.throughput -61.3% regression
Date: Mon, 3 Dec 2018 12:26:28 -0800 (PST)
Message-ID: <alpine.DEB.2.21.1812031210490.192288@chino.kir.corp.google.com> (raw)
In-Reply-To: <20181203192344.GA2986@redhat.com>

On Mon, 3 Dec 2018, Andrea Arcangeli wrote:

> It's trivial to reproduce the badness by running a memhog process that
> allocates more than the RAM of 1 NUMA node, under defrag=always
> setting (or by changing memhog to use MADV_HUGEPAGE) and it'll create
> swap storms despite 75% of the RAM is completely free in a 4 node NUMA
> (or 50% of RAM free in a 2 node NUMA) etc..
> 
> How can it be ok to push the system into gigabytes of swap by default
> without any special capability despite 50% - 75% or more of the RAM is
> free? That's the downside of the __GFP_THISNODE optimizaton.
> 

The swap storm is the issue that is being addressed.  If your remote 
memory is as low as local memory, the patch to clear __GFP_THISNODE has 
done nothing to fix it: you still get swap storms and memory compaction 
can still fail if the per-zone freeing scanner cannot utilize the 
reclaimed memory.  Recall that this patch to clear __GFP_THISNODE was 
measured by me to have a 40% increase in allocation latency for fragmented 
remote memory on Haswell.  It makes the problem much, much worse.

> __GFP_THISNODE helps increasing NUMA locality if your app can fit in a
> single node which is the common David's workload. But if his workload
> would more often than not fit in a single node, he would also run into
> an unacceptable slowdown because of the __GFP_THISNODE.
> 

Which is why I have suggested that we do not do direct reclaim, as the 
page allocator implementation expects all thp page fault allocations to 
have __GFP_NORETRY set, because no amount of reclaim can be shown to be 
useful to the memory compaction freeing scanner if it is iterated over by 
the migration scanner.

> I think there's lots of room for improvement for the future, but in my
> view that __GFP_THISNODE as it was implemented was an incomplete hack,
> that opened the door for bad VM corner cases that should not happen.
> 

__GFP_THISNODE is intended specifically because of the remote access 
latency increase that is encountered if you fault remote hugepages over 
local pages of the native page size.

  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 [this message]
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
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=alpine.DEB.2.21.1812031210490.192288@chino.kir.corp.google.com \
    --to=rientjes@google.com \
    --cc=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=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