Re: kupdated using all CPU

[ebiederm@xmission.com (Eric W. Biederman)]

Andrew Morton <akpm@zip.com.au> writes:

> john wrote:
> > 
> > [Mon, Feb 18, 2002 at 02:13:06PM -0800] akpm@zip.com.au wrote:
> > + john wrote:
> > + >
> > + > hi,
> > + > ive searched all over and found many references to this problem, but
> > + > never found an actual solution.  the problem is that during heavy
> > + > disk I/O, kupdated will periodically take up ALL the cpu.
> > +
> > + I've seen a couple of reports of this, nothing to indicate that it's
> > + a common problem?
> > +
> > + In the other reports, it was related to extremely low disk throughput.
> > + What does `hdparm -t /dev/hda' say?
> > 
> > root@doom:~# hdparm -t /dev/hda
> > 
> > /dev/hda:
> >  Timing buffered disk reads:  64 MB in 25.60 seconds =  2.50 MB/sec
> 
> ugh.  OK, I'll see if I cen reproduce this - there's no reason
> why disk suckiness should cause high CPU load.  But you need to
> pay some attention to your IDE settings in kernel config, and
> possibly tuning.


Another possibility with the same symptoms is that there are simply
very large I/O request starving everything else out.  When some
crucial data needs to be paged back in.  john can you confirm you
looked in top and saw kupdate taking 100% of the cpu?

Eric