[Lustre-devel] COS performance issues

Andreas Dilger adilger at sun.com
Sat Oct 11 09:00:10 PDT 2008

On Oct 08, 2008  15:44 +0400, Alexander Zarochentsev wrote:
> I think the problem is that COS defers processing of replies to
> transaction commit time.  When commit happens, MDS has to process
> thousands of replies (about 14k replies per commit in the test 3.a)
> in short period of time. I guess the mdt service threads all woken
> up and spin trying to get the service svr_lock. Processing of new
> requests may also suffer of this.

Can you please explain what replies are being blocked?  It can't be the
create replies or the clients would be blocked waiting after starting a
single create each.

I think the thread and lock contention is only part of the issue - if all
of these replies are blocked until transaction commit this wastes all of
the bandwidth on the network while the replies are being held.

Cheers, Andreas
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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