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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
Date: Mon, 26 Jul 2004 16:29:50 -0700	[thread overview]
Message-ID: <20040726162950.7f4a3cf4.akpm@osdl.org> (raw)
In-Reply-To: <E1BmKAd-0001hz-00@dorka.pomaz.szeredi.hu>

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?

  reply	other threads:[~2004-07-26 23:31 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-07-18 22:30 [PATCH] fix readahead breakage for sequential after random reads Miklos Szeredi
2004-07-26 23:29 ` Andrew Morton [this message]
2004-07-26 23:56   ` Ram Pai
2004-07-27  0:08     ` Andrew Morton
2004-07-27  4:18       ` Ram Pai
2004-07-27  7:40         ` Miklos Szeredi
2004-07-27 15:34           ` Ram Pai
2004-08-04 17:38         ` Ram Pai
2004-08-04 19:39           ` Shane Shrybman

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