Re: 2.6.4 : 100% CPU use on EIDE disk operarion, VIA chipset

Mikhail Ramendik
2004-04-04T19:58:05Z

Hello,

Andreas Hartmann wrote:
> > As recommended there, I have tried 2.6.5-rc3-mm4.
> >
> > No change. Still 100% CPU usage; the performance seems teh same.
>
> Yes. But it's curious:
> Take a tar-file, e.g. tar the compiled 2.6 kernel directory. Than, untar
> it again - the machine behaves total normaly.

Not really. I tried a "simple" tar (no gzib/bzip2) - it was the same as
with cp, a near-100% CPU "system" load, most of it iowait.

If I use bzip2 with tar, then yes, the load is nearly 100% "user",
actually it's bzip2. But this is because the disk i/o is done at a *far*
slower rate; the bottleneck is the CPU. If we don't read (or write) the
disk heavily, naturally the system/iowait load is low.

I tried doing a "cp" in another xterm window, while the tar/bzip2 was
running. And sure enough, up the CPU system/iowait usage goes - the
"cp"'s disk i/o takes much of the CPU time away from the bz2 task! Looks
exactly like a cause of performance problems.

(All of this was done on 2.6.5-rc3-mm4).

Yours, Mikhail Ramendik

> And the 2.6-kernel is about
> 23% faster than the 2.4-kernel.
>
>
> > Yours, Mikhail Ramendik
> >
> > P.S. Sorry for making all comments into answers to your letter. I just
> > don't want to break the thread.
>
> No problem - it's easier to read with comment directly in the text.
>
>
> Regards,
> Andreas Hartmann
>
>