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

Lehmann
2001-08-25T23:35:02Z

On Sat, Aug 25, 2001 at 10:33:36PM +0100, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
> > exactly this is a point: my disk can do 5mb/s with almost random seeks,
> > and linux indeed reads 5mb/s from it. but the userpsace process doing
> > read() only ever sees 2mb/s because the kernel throes away all the nice
> > pages.
>
> Which means the VM in the relevant kernel is probably crap or your working
> set exceeds ram.

The relevant kernel is linux (all 2.4 versions I tested), and no, working
set exceeding ram should never result in such excessive thrashing. So yes,
the VM in the kernel is crap (in this particular case, namely high-volume
fileserving) ;)

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