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Date: Thu, 07 Mar 2002 12:56:44 -0800
From: Andrew Morton <akpm@zip.com.au>
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To: Rik van Riel <riel@conectiva.com.br>
CC: Daniel Phillips <phillips@bonn-fries.net>,
        Alan Cox <alan@lxorguk.ukuu.org.uk>, yodaiken@fsmlabs.com,
        Jeff Dike <jdike@karaya.com>, Benjamin LaHaise <bcrl@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org
Subject: Re: [RFC] Arch option to touch newly allocated pages
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Rik van Riel wrote:
> 
> On Thu, 7 Mar 2002, Andrew Morton wrote:
> > Daniel Phillips wrote:
> > >
> > > a GFP flag that says 'fail if this looks hard to get'.
> >
> > Something like that would provide a solution to the
> > readahead thrashing problem.
> 
> Nope.  Readahead pages are clean and very easy to evict, so
> it's still trivial to evict all the pages from another readahead
> window because everybody's readahead window is too large.
> 

I was thinking an explicit GFP_READAHEAD and PG_readahead.
Where a GFP_READAHEAD allocation would fail if it can't 
find any non-readahead pages.  And it would fail if it
had to perform I/O.

That's not nice - it'd result in large LRU walks.  But it'd
be better than the 10x slowdown which readahead thrashing
causes.

Any clever ideas?

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