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Re: [PATCH 2/3] mm: filemap: only do access activations on reads

From Andrew Morton <akpm@linux-foundation.org>
Newsgroups linux.kernel
Subject Re: [PATCH 2/3] mm: filemap: only do access activations on reads
Date 2016-04-04 23:30 +0200
Message-ID <rkken-Rn-9@gated-at.bofh.it> (permalink)
References <rkgkq-6rb-15@gated-at.bofh.it> <rkgkq-6rb-23@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Mon,  4 Apr 2016 13:13:37 -0400 Johannes Weiner <hannes@cmpxchg.org> wrote:

> Andres Freund observed that his database workload is struggling with
> the transaction journal creating pressure on frequently read pages.
> 
> Access patterns like transaction journals frequently write the same
> pages over and over, but in the majority of cases those pages are
> never read back. There are no caching benefits to be had for those
> pages, so activating them and having them put pressure on pages that
> do benefit from caching is a bad choice.

Read-after-write is a pretty common pattern: temporary files for
example.  What are the opportunities for regressions here?

Did you consider providing userspace with a way to hint "this file is
probably write-then-not-read"?

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Thread

[PATCH 0/3] mm: support bigger cache workingsets and protect against writes Johannes Weiner <hannes@cmpxchg.org> - 2016-04-04 19:20 +0200
  [PATCH 2/3] mm: filemap: only do access activations on reads Johannes Weiner <hannes@cmpxchg.org> - 2016-04-04 19:20 +0200
    Re: [PATCH 2/3] mm: filemap: only do access activations on reads Andrew Morton <akpm@linux-foundation.org> - 2016-04-04 23:30 +0200
      Re: [PATCH 2/3] mm: filemap: only do access activations on reads Rik van Riel <riel@redhat.com> - 2016-04-04 23:40 +0200
        Re: [PATCH 2/3] mm: filemap: only do access activations on reads Andrew Morton <akpm@linux-foundation.org> - 2016-04-05 00:00 +0200
        Re: [PATCH 2/3] mm: filemap: only do access activations on reads Johannes Weiner <hannes@cmpxchg.org> - 2016-04-05 20:00 +0200
      Re: [PATCH 2/3] mm: filemap: only do access activations on reads Johannes Weiner <hannes@cmpxchg.org> - 2016-04-05 00:50 +0200
  Re: [PATCH 0/3] mm: support bigger cache workingsets and protect  against writes Andres Freund <andres@anarazel.de> - 2016-04-04 21:00 +0200

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