On 07/01/2012 08:07 PM, Dave Chinner wrote: > On Thu, Jun 28, 2012 at 06:52:56AM -0400, Brian Foster wrote: >> xfsaild idle mode logic currently leads to a couple hangs: >> >> 1.) If xfsaild is rescheduled in during an incremental scan >> (i.e., tout != 0) and the target has been updated since >> the previous run, we can hit the new target and go into >> idle mode with a still populated ail. >> 2.) A wake up is only issued when the target is pushed forward. >> The wake up can race with xfsaild if it is currently in the >> process of entering idle mode, causing future wake up >> events to be lost. >> >> These hangs have been reproduced and verified as fixed by >> running xfstests 273 in a loop on a slightly modified upstream >> kernel. The kernel is modified to re-enable idle mode as >> previously implemented (when count == 0) and with a revert of >> commit 670ce93f, which includes performance improvements that >> make this harder to reproduce. >> >> The solution, the algorithm for which has been outlined by >> Dave Chinner, is to modify xfsaild to enter idle mode only when >> the ail is empty and the push target has not been moved forward >> since the last push. >> >> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx> > > Looks OK to me, and hasn't caused any problems here. > > Final question - did you confirm with powertop that the xfsaild is > no longer causing wakeups a minute or two after you stop writing to > the filesystem? (I haven't yet) > I hadn't tested with powertop, but I had some tracepoints hacked in around the idle/wake cases to verify the thread was actually scheduling out. FWIW, I just gave powertop a quick test and it appears to work as expected... With current upstream on my rhel6.3 VM, I see the following after running a 'touch /mnt/file;sync' and letting the fs idle for a bit: 0.5% ( 19.9) xfsaild/vdb1 : xfsaild (process_timeout) and this drops off completely with the patch applied. Thanks for the tip. Brian > Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx> > _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
