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SubjectRe: [PATCH] fix readahead breakage for sequential after random reads
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Andrew,
Yes the patch fixes a valid bug.


RP

On Mon, 2004-07-26 at 16:29, Andrew Morton wrote:
> 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?
>

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