lkml.org 
[lkml]   [2015]   [Feb]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH] mm: madvise: Ignore repeated MADV_DONTNEED hints
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:

> 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.


\
 
 \ /
  Last update: 2015-02-03 00:01    [W:0.297 / U:0.116 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site