From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Dilger Date: Sat, 11 Oct 2008 10:00:10 -0600 Subject: [Lustre-devel] COS performance issues In-Reply-To: <200810081544.08292.alexander.zarochentsev@sun.com> References: <200810081544.08292.alexander.zarochentsev@sun.com> Message-ID: <20081011160010.GR2009@webber.adilger.int> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lustre-devel@lists.lustre.org 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.