On Tue, Mar 26, 2013 at 06:14:30PM +0800, Jeff Liu wrote: > On 03/12/2013 08:05 PM, Dave Chinner wrote: > > On Tue, Mar 12, 2013 at 07:56:35PM +0800, Jeff Liu wrote: > >> More info, 3.7.0 is the oldest kernel on my environment, I ran into the > >> same problem. > > > > Thanks for following up so quickly, Jeff. So the problem is that a > > new test is tripping over a bug that has been around for a while, > > not that it is a new regression. > > > > OK, so I'll expunge that from my testing for the moment as I don't > > ahve time to dig in and find out what the cause is right now. If > > anyone else wants to.... :) > > I did some further tests to nail down this issue, just posting the analysis result here, > it might be of some use when we revising it again. > > The disk is formated with Dave's previous comments, i.e. > mkfs.xfs -f -b size=512 -d agcount=16,su=256k,sw=12 -l su=256k,size=2560b /dev/xxx > > First of all, looks this bug stayed in hiding for years since I can reproduce it between upstream > 3.0 to 3.9.0-rc3, the oldest kernel I have tried is 2.6.39 which has the same problem. If you mount 2.6.39 with "-o nodelaylog", does the problem go away? > IMHO, looks the major cause is related to the 'sunit' parameter, > since it would affect the log space unit calculations by > '2*log->l_mp->m_sb.sb_logsunit' at xlog_ticket_alloc(). However, > we don't include this factor into consideration at mkfs or mount > stage, should we take it into account? That's what I suspected was the problem. i.e. that the log was too small for the given configuration. The question is this: how much space do we need to reserve. I'm thinking a minimum of 4*lsu - 2*lsu for the existing CIL context, and another 2*lsu for any queued ticket waiting for space to come available. I haven't thought a lot about it, though, and I have a little demon sitting on my shoulder nagging me about specific thresholds whether they need to play a part in this. e.g. no single transaction can be larger than half the log; AIL push thresholds of 25% of log space; background CIL commit threshold of 12.5% of the log... So it's not immediately clear to me how much bigger the log needs to be... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
