[Gluster-users] Concurrency limitation?

[Jeff Darcy]

On Tue, 7 Feb 2012 14:44:16 +0000
Brian Candler <B.Candler at pobox.com> wrote:

> On Tue, Feb 07, 2012 at 08:18:24AM -0600, Greg Swift wrote:
> >    concurrency will be affected by your underlying filesystem as
> > well. which filesystem you got?
> 
> XFS. But as I said, I am comparing direct-to-filesystem versus
> via-gluster-to-same-filesystem.
> 
> I have been digging through source code. If I am reading it right, it
> seems that xlators/performance/io-threads only sets the number of
> threads to be log(base2) of the number of outstanding I/O entries in
> the queue.  That is, to get 8 concurrent threads you need 256
> outstanding requests in the queue.

FWIW, I've also wondered sometimes whether we increase this count
aggressively enough.  At first blush, it seems that we should be
increasing the thread count whenever the queue is staying full and the
last increment improved our iowait/idle ratio.  I'd be very curious to
hear about your results.