Message-ID: <43564D8F.3000809@argo.co.il>
Date: Wed, 19 Oct 2005 15:43:43 +0200
From: Avi Kivity <avi@argo.co.il>
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CC: Badari Pulavarty <pbadari@gmail.com>, Guido Fiala <gfiala@s.netic.de>,
       lkml <linux-kernel@vger.kernel.org>
Subject: Re: large files unnecessary trashing filesystem cache?
References: <4Z5WG-1iM-19@gated-at.bofh.it> <4Z6zs-27l-39@gated-at.bofh.it> <E1ERzTq-0001IA-Ba@be1.lrz>
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Bodo Eggert wrote:

>I guess the solution would be using random cache eviction rather than
>a FIFO. I never took a look the cache mechanism, so I may very well be
>wrong here.
>  
>
Instead of random cache eviction, you can make pages that were read in 
contiguously age faster than pages that were read in singly.

The motivation is that the cost of reading 64K vs 4K is almost the same 
(most of the cost is the seek), while the benefit for evicting 64K is 16 
times that of evicting 4K. Over time, the kernel would favor expensive 
random-access pages over cheap streaming pages.

In a way, this is already implemented for inodes, which are aged more 
slowly than data pages.


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