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Date: Mon, 26 Jul 2004 16:29:50 -0700
From: Andrew Morton <akpm@osdl.org>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: linux-kernel@vger.kernel.org, Ram Pai <linuxram@us.ibm.com>
Subject: Re: [PATCH] fix readahead breakage for sequential after random
 reads
Message-Id: <20040726162950.7f4a3cf4.akpm@osdl.org>
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References: <E1BmKAd-0001hz-00@dorka.pomaz.szeredi.hu>
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Miklos Szeredi <miklos@szeredi.hu> wrote:
>
> Current readahead logic is broken when a random read pattern is
>  followed by a long sequential read.  The cause is that on a window
>  miss ra->next_size is set to ra->average, but ra->average is only
>  updated at the end of a sequence, so window size will remain 1 until
>  the end of the sequential read.
> 
>  This patch fixes this by taking the current sequence length into
>  account (code taken from towards end of page_cache_readahead()), and
>  also setting ra->average to a decent value in handle_ra_miss() when
>  sequential access is detected.

Thanks.   Do you have any performance testing results from this patch?