On Thu, Feb 10, 2011 at 10:42:54PM +0200, Petre Rodan wrote: > > Hello Dave, > > On Fri, Jan 21, 2011 at 10:43:10AM +1100, Dave Chinner wrote: > > ..... > > > in other words xfsyncd and xfsbufd now alternate at 18s intervals > > > keeping the drive busy with nothing constructive hours after the > > > last write to the drive. > > > > This is a different problem, and not one I've seen before. Looking > > at the traces, it appears that we have not empties the AIL. At > > least, that's what I'm assuming at this point because log IO > > completion is not updating log tail. When we start a log IO, we set > > the log header lsn to the current head: > > > > > xfssyncd/sdc1-1413 [000] 3356.093456: xfs_log_reserve: dev 8:33 type DUMMY1 t_ocnt 1 t_cnt 1 t_curr_res 2740 t_unit_res 2740 t_flags XLOG_TIC_INITED reserveq empty writeq empty grant_reserve_cycle 2 grant_reserve_bytes 428523008 grant_write_cycle 2 grant_write_bytes 428523008 curr_cycle 2 curr_block 836959 tail_cycle 2 tail_block 810683 > > > > Which in this case is: curr_cycle 2 curr_block 836959 > > > > When the log IO completes, that value gets written to the > > l_last_sync_lsn. When the AIL tail is removed, the tail lsn is > > updated to the new tail item. If the AIL is empty, then the > > l_last_sync_lsn is used. That means then next dummy transaction > > made to cover the log should have the cycle/block of the above > > current cycle. > > > > Instead, what I see is that the next dummmy transaction shows: > > > > > xfssyncd/sdc1-1413 [000] 3392.067122: xfs_log_reserve: dev 8:33 type DUMMY1 t_ocnt 1 t_cnt 1 t_curr_res 2740 t_unit_res 2740 t_flags XLOG_TIC_INITED reserveq empty writeq empty grant_reserve_cycle 2 grant_reserve_bytes 428524032 grant_write_cycle 2 grant_write_bytes 428524032 curr_cycle 2 curr_block 836961 tail_cycle 2 tail_block 810683 > > > > The current head has moved: curr_cycle 2 curr_block 836961 > > > > But the tail hasn't: tail_cycle 2 tail_block 810683 > > > > So effectively we've got some item on the AIL that we haven't > > flushed and isn't being flushed by xfssyncd. That's the problem I > > need to get to the bottom of and it also explains why it's an > > intermitten problem... > > I have been watching the stream of patches that go into 2.6.38, > but I probably missed the one that might be the answer to the > problem above. can you please tell me which one to try, or can I > help with anything? I know what the problem is, but I haven't had time to work out of code a fix. Been spending my time trying to work out the cause bugs that are triggering hangs, crashes or corruptions here... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
