Re: kupdated using all CPU

[john <john@zlilo.com>]

[Mon, Feb 18, 2002 at 09:53:08PM -0700] ebiederm@xmission.com wrote:
+ 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?

yes, i did.  another thing that makes it pretty obvious is the cpu time reported by ps.  kupdated cpu time will stay 0:00 until i run into the condition i described.  then kupdated cpu time will jump as much as 0:45.

but i have fixed the issue by using the correct ide driver.  though, someone may want to look into this anyway...dunno..
-j