LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Mel Gorman <mgorman@suse.de>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Dave Hansen <dave.hansen@intel.com>,
	linux-mm@kvack.org, Minchan Kim <minchan@kernel.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] mm: madvise: Ignore repeated MADV_DONTNEED hints
Date: Tue, 3 Feb 2015 11:21:24 +0000	[thread overview]
Message-ID: <20150203112124.GS2395@suse.de> (raw)
In-Reply-To: <20150203104756.GB14259@node.dhcp.inet.fi>

On Tue, Feb 03, 2015 at 12:47:56PM +0200, Kirill A. Shutemov wrote:
> On Tue, Feb 03, 2015 at 09:47:18AM +0000, Mel Gorman wrote:
> > On Mon, Feb 02, 2015 at 02:22:36PM -0800, Dave Hansen wrote:
> > > On 02/02/2015 08:55 AM, Mel Gorman wrote:
> > > > This patch identifies when a thread is frequently calling MADV_DONTNEED
> > > > on the same region of memory and starts ignoring the hint. On an 8-core
> > > > single-socket machine this was the impact on ebizzy using glibc 2.19.
> > > 
> > > The manpage, at least, claims that we zero-fill after MADV_DONTNEED is
> > > called:
> > > 
> > 
> > It also claims that the kernel is free to ignore the advice.
> > 
> > > >      MADV_DONTNEED
> > > >               Do  not  expect  access in the near future.  (For the time being, the application is finished with the given range, so the kernel can free resources
> > > >               associated with it.)  Subsequent accesses of pages in this range will succeed, but will result either in reloading of the memory contents  from  the
> > > >               underlying mapped file (see mmap(2)) or zero-fill-on-demand pages for mappings without an underlying file.
> > > 
> > > So if we have anything depending on the behavior that it's _always_
> > > zero-filled after an MADV_DONTNEED, this will break it.
> > 
> > True. I'd be surprised if any application depended on that 
> 
> IIUC, jemalloc depends on this[1].
> 
> [1] https://github.com/jemalloc/jemalloc/blob/dev/src/chunk_mmap.c#L117
> 

Hope they never back regions with hugetlb then or fall apart if the process
called mlockall

-- 
Mel Gorman
SUSE Labs

      reply	other threads:[~2015-02-03 11:21 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-02 16:55 Mel Gorman
2015-02-02 22:05 ` Andrew Morton
2015-02-02 22:18   ` Mel Gorman
2015-02-02 22:35     ` Andrew Morton
2015-02-03  0:26       ` Davidlohr Bueso
2015-02-03 10:50       ` Mel Gorman
2015-02-05 21:44     ` Rik van Riel
2015-02-02 22:22 ` Dave Hansen
2015-02-03  8:19   ` MADV_DONTNEED semantics? Was: " Vlastimil Babka
2015-02-03 10:53     ` Kirill A. Shutemov
2015-02-03 11:42       ` Vlastimil Babka
2015-02-03 16:20         ` Michael Kerrisk (man-pages)
2015-02-04 13:46           ` Vlastimil Babka
2015-02-04 14:00             ` Michael Kerrisk (man-pages)
2015-02-04 17:02               ` Vlastimil Babka
2015-02-04 19:24                 ` Michael Kerrisk (man-pages)
2015-02-05  1:07                   ` Minchan Kim
2015-02-06 15:41                     ` Michael Kerrisk (man-pages)
2015-02-09  6:46                       ` Minchan Kim
2015-02-09  9:13                         ` Michael Kerrisk (man-pages)
2015-02-05 15:41                   ` Michal Hocko
2015-02-06 15:57                     ` Michael Kerrisk (man-pages)
2015-02-06 20:45                       ` Michal Hocko
2015-02-09  6:50                       ` Minchan Kim
2015-02-04  0:09         ` Minchan Kim
2015-02-03 11:16     ` Mel Gorman
2015-02-03 15:21       ` Michal Hocko
2015-02-03 16:25         ` Michael Kerrisk (man-pages)
2015-02-03  9:47   ` Mel Gorman
2015-02-03 10:47     ` Kirill A. Shutemov
2015-02-03 11:21       ` Mel Gorman [this message]

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=20150203112124.GS2395@suse.de \
    --to=mgorman@suse.de \
    --cc=akpm@linux-foundation.org \
    --cc=dave.hansen@intel.com \
    --cc=kirill@shutemov.name \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=minchan@kernel.org \
    --cc=vbabka@suse.cz \
    --subject='Re: [RFC PATCH] mm: madvise: Ignore repeated MADV_DONTNEED hints' \
    /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).