Re: [resent PATCH] Re: very slow parallel read performance

Lehmann
2001-08-26T02:57:46Z

On Sat, Aug 25, 2001 at 11:02:25PM -0300, Rik van Riel <riel@conectiva.com.br> wrote:
> This is because the readahead windows are too large so the
> kernel ends up evicting data before its needed and has to
> re-read the data.
>
> Also see http://linux-mm.org/wiki/moin.cgi/StreamingIo
> in the Linux-MM wiki.

O_STREAMING is an interesting idea (I talked with stefan traby about
the problem and we came to a similar conclusion - fadvise instead of
madvise, and per-file characteristics as opposed to blockdevices or global
settings).

Anyway, so far it really looks as if this is the case - there is some
limit (around 700 conns) where the available memory doesn't suffice for
read-ahead.

> This problem should be relatively easy to fix for 2.4.

Nice ;)

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