Re: ioflush kernel thread chewing CPU time

[Simon Burge <simonb%NetBSD.org@localhost>]

Andrew Doran wrote:

> On Wed, Mar 25, 2009 at 12:56:59PM +1100, Simon Burge wrote:
> 
> > Simon Burge wrote:
> > 
> > > [ profiling working with enami's patch ]
> > 
> > I've got two 30-second profiles while I'm seeing ioflush using a lot
> > of CPU time.  With a profiled kernel I'm seeing ioflush use about 30-35%
> > instead of the "normal" 20%.  The first of these is with top running,
> > the second while the machine should be otherwise completely idle:
> > 
> >   ftp://ftp.netbsd.org/pub/NetBSD/misc/simonb/ioflush-gmon.txt.A.bz2
> >   ftp://ftp.netbsd.org/pub/NetBSD/misc/simonb/ioflush-gmon.txt.B.bz2
> > 
> > I've not looked at them myself yet...
> 
> Those were very useful, thanks. I have committed another set of fixes.
> Can you try running with them and see if the problem still occurs?

After 1 days 20 hours this seems better, but I'm still not sure if the
"problem" is totally fixed.  Right now top shows ioflush using about 3%
of CPU time, and it's used about 84 mins since boot:

  PID   LID USERNAME PRI STATE      TIME   WCPU    CPU COMMAND      NAME
    0    49 root     124 syncer/0  84:28  3.08%  3.08% [system]     ioflush

I've only updated my kernel to netbsd-5, but still have old userland.
I'm tempted to put the old kernel back and see if this amount of CPU
usage for ioflush is "normal" or not...

Cheers,
Simon.