linux-kernel - Re: madvise(2) MADV

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Message-ID: <487F89AE.9070007@redhat.com>
Date:	Thu, 17 Jul 2008 14:04:30 -0400
From:	Chris Snook <csnook@...hat.com>
To:	Rik van Riel <riel@...hat.com>
CC:	Nick Piggin <nickpiggin@...oo.com.au>,
	Eric Rannaud <eric.rannaud@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: madvise(2) MADV_SEQUENTIAL behavior

Rik van Riel wrote:
> On Thu, 17 Jul 2008 16:14:29 +1000
> Nick Piggin <nickpiggin@...oo.com.au> wrote:
> 
>>> It might encourage user space applications to start using
>>> FADV_SEQUENTIAL or FADV_NOREUSE more often (as it would become
>>> worthwhile to do so), and if they do (especially cron jobs), the problem
>>> of the slow desktop in the morning would progressively solve itself.
>> The slow desktop in the morning should not happen even without such a
>> call, because the kernel should not throw out frequently used data (even
>> if it is not quite so recent) in favour of streaming data.
>>
>> OK, I figure it doesn't do such a good job now, which is sad, 
> 
> Do you have any tests in mind that we could use to decide
> whether the patch I posted Tuesday would do a decent job
> at protecting frequently used data from streaming data?
> 
> http://lkml.org/lkml/2008/7/15/465
> 

1) start up a memory-hogging Java app
2) run a full-system backup

If it works well, the Java app shouldn't slow down much.

-- Chris
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