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SubjectRe: [PATCH] Re: PATCH: killing read_ahead[]


Rik van Riel wrote:
>
> On Wed, 25 Oct 2000, Jeff V. Merkey wrote:
>
> > I've reviewed the patch. It's affect seems minimal and will not
> > break NWFS as proposed -- it looks like, however, it will reduce
> > the performance slightly of EXT2/3 with iozone for read ahead
> > since the first section of the patch limits the read ahead
> > window size.
>
> Ummm, please read it again ;)
>
> The patch actually /increases/ the readahead size when
> we start to read a file from the beginning.

But only if the file is smaller than MIN_READAHEAD * 2, which would be
the case for small files (which would read the whole file anyway, which
is how the page cache behaves today anyway).

?* If we start reading from the beginning of the file, read in
MIN_READAHEAD pages. Note
that if the file is smaller then MIN_READAHEAD * 2 limiting ourselves to
MIN_READAHEAD would
result in one "too small" IO

(there's that fixed block size crap biting us in the ass again)

so in that case, just read the whole file.

:-)

Jeff

>
> regards,
>
> Rik
> --
> "What you're running that piece of shit Gnome?!?!"
> -- Miguel de Icaza, UKUUG 2000
>
> http://www.conectiva.com/ http://www.surriel.com/
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