Re: Context switching and Xeon processors

t == tgl@sss.pgh.pa.us writes:

 t> "Brandon Metcalf" <bmetcalf@nortel.com> writes:
 t> > We've been tuning the kernel (2.4 SMP flavor) and have improved
 t> > performance quite a bit.  I'm now wondering if turning off HT will
 t> > improve performance even more.  Based on the vmstat output below, is
 t> > the context switching typical or too high?

 t> Given that your CPU usage is hovering around 2%, it's highly unlikely
 t> that you'll be able to measure any change at all by fiddling with HT.
 t> What you need to be working on is disk I/O --- the "80% wait" number
 t> is what should be getting your attention, not the CS number.

 t> (FWIW, on the sort of hardware you're talking about, I wouldn't worry
 t> about CS rates lower than maybe 10000/sec --- the hardware can sustain
 t> well over 10x that.)


Yes, I agree the disk I/O is an issue and that's what we've been
addressing with the tuning we've been doing and have been able to
improve.  I think that we really need to go to a RAID 10 array to
address the I/O issue, but thought I would investigate the context
switching issue.

Thanks for the information.

--
Brandon