On Thu, Feb 23, 2012 at 11:54:18AM +0100, Jan Kara wrote: > On Thu 23-02-12 11:48:53, Jan Kara wrote: > > Hello, > > > > when I run: > > while true; do ~/tests/xfstests-dev/ltp/fsstress -d /mnt -n 10000 -p 4; done > > > > and in parallel > > > > while true; do ./fsfreeze /mnt; sync; ./fsfreeze -u /mnt; sleep 3; done > > > > where fsfreeze is a small utility freezing and unfreezing filesystem. Ah, the world has been reinvented again: $ xfs_io -x -c "help freeze" -c "help thaw" freeze -- freeze filesystem of current file thaw -- unfreeze filesystem of current file > > I get > > warnings like: > BTW, the first message is: > [ 1626.278347] XFS (vdb1): xlog_space_left: head behind tail > [ 1626.278349] tail_cycle = 7, tail_bytes = 12907008 > [ 1626.278351] GH cycle = 7, GH bytes = 12907000 So out by 8 bytes. This is indicative of a transaction reservation accounting error or a race condition in updating the grant heads during transaction reservation/completion. > > [ 2029.103193] XFS (vdb1): xlog_space_left: head behind tail > > [ 2029.103195] tail_cycle = 10, tail_bytes = 6036480 > > [ 2029.103197] GH cycle = 10, GH bytes = 6035728 and 400s later is it out by 752 bytes > > [ 2029.103218] XFS (vdb1): xlog_space_left: head behind tail > > [ 2029.103219] tail_cycle = 10, tail_bytes = 6036480 > > [ 2029.103220] GH cycle = 10, GH bytes = 6035728 > > [ 2033.269796] XFS (vdb1): xlog_space_left: head behind tail > > [ 2033.269800] tail_cycle = 10, tail_bytes = 6400512 > > [ 2033.269803] GH cycle = 10, GH bytes = 6399752 And 4s later (a single freeze) it is out by 760 bytes. Ok, so that looks like a 8 byte accounting leak rather than a race that is occurring. Given that it has been roughly 400s since the first report, and you're running a freeze roughly every 4s, that's 100 freezes, and that's roughly 800 bytes which is in the ballpark for 8 bytes a freeze being leaked. I'll look into it further. > Is it a real problem or just annoyance? Real problem, but something rather unlikely to be tripped over in the real world.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
