Re: [PATCH] fix readahead breakage for sequential after randomreads

[Andrew Morton]

Miklos Szeredi <miklos@xxxxxxxxxx> 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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