Re: high latency NFS

[Dave Chinner <david@fromorbit.com>]

On Fri, Aug 01, 2008 at 03:15:59PM -0400, J. Bruce Fields wrote:
> On Fri, Aug 01, 2008 at 05:23:20PM +1000, Dave Chinner wrote:
> > On Thu, Jul 31, 2008 at 05:03:05PM +1000, Neil Brown wrote:
> > > You might want to track the max length of the request queue too and
> > > start more threads if the queue is long, to allow a quick ramp-up.
> > 
> > Right, but even request queue depth is not a good indicator. You
> > need to leep track of how many NFSDs are actually doing useful
> > work. That is, if you've got an NFSD on the CPU that is hitting
> > the cache and not blocking, you don't need more NFSDs to handle
> > that load because they can't do any more work than the NFSD
> > that is currently running is. 
> > 
> > i.e. take the solution that Greg banks used for the CPU scheduler
> > overload issue (limiting the number of nfsds woken but not yet on
> > the CPU),
> 
> I don't remember that, or wasn't watching when it happened.... Do you
> have a pointer?

Ah, I thought that had been sent to mainline because it was
mentioned in his LCA talk at the start of the year. Slides
65-67 here:

http://mirror.linux.org.au/pub/linux.conf.au/2007/video/talks/41.pdf

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com