On Fri, Nov 13, 2009 at 01:40:04PM -0500, Chris Mason wrote: > On Fri, Nov 13, 2009 at 05:34:46PM +0000, Mel Gorman wrote: > > On Fri, Nov 13, 2009 at 07:58:12AM -0500, Chris Mason wrote: > > > This is still likely to set your dm data on fire. It is only meant for > > > testers that start with mkfs and don't have any valuable dm data. > > > > > > > The good news is that my room remains fire-free. Despite swap also > > running from dm-crypt, I had no corruption or instability issues. > > Ok, definitely not so convincing I'd try and shove it into a late rc. > > > > > Here is an updated set of results for fake-gitk running. > > > > X86 > > 2.6.30-0000000-force-highorder Elapsed:12:08.908 Failures:0 > > 2.6.31-0000000-force-highorder Elapsed:10:56.283 Failures:0 > > 2.6.31-0000006-dm-crypt-unplug Elapsed:11:51.653 Failures:0 > > 2.6.31-0000012-pgalloc-2.6.30 Elapsed:12:26.587 Failures:0 > > 2.6.31-0000123-congestion-both Elapsed:10:55.298 Failures:0 > > 2.6.31-0001234-kswapd-quick-recheck Elapsed:18:01.523 Failures:0 > > 2.6.31-0123456-dm-crypt-unplug Elapsed:10:45.720 Failures:0 > > 2.6.31-revert-8aa7e847 Elapsed:15:08.020 Failures:0 > > 2.6.32-rc6-0000000-force-highorder Elapsed:16:20.765 Failures:4 > > 2.6.32-rc6-0000006-dm-crypt-unplug Elapsed:13:42.920 Failures:0 > > 2.6.32-rc6-0000012-pgalloc-2.6.30 Elapsed:16:13.380 Failures:1 > > 2.6.32-rc6-0000123-congestion-both Elapsed:18:39.118 Failures:0 > > 2.6.32-rc6-0001234-kswapd-quick-recheck Elapsed:15:04.398 Failures:0 > > 2.6.32-rc6-0123456-dm-crypt-unplug Elapsed:12:50.438 Failures:0 > > 2.6.32-rc6-revert-8aa7e847 Elapsed:20:50.888 Failures:0 > > > > X86-64 > > 2.6.30-0000000-force-highorder Elapsed:10:37.300 Failures:0 > > 2.6.31-0000000-force-highorder Elapsed:08:49.338 Failures:0 > > 2.6.31-0000006-dm-crypt-unplug Elapsed:09:37.840 Failures:0 > > 2.6.31-0000012-pgalloc-2.6.30 Elapsed:15:49.690 Failures:0 > > 2.6.31-0000123-congestion-both Elapsed:09:18.790 Failures:0 > > 2.6.31-0001234-kswapd-quick-recheck Elapsed:08:39.268 Failures:0 > > 2.6.31-0123456-dm-crypt-unplug Elapsed:08:20.965 Failures:0 > > 2.6.31-revert-8aa7e847 Elapsed:08:07.457 Failures:0 > > 2.6.32-rc6-0000000-force-highorder Elapsed:18:29.103 Failures:1 > > 2.6.32-rc6-0000006-dm-crypt-unplug Elapsed:25:53.515 Failures:3 > > 2.6.32-rc6-0000012-pgalloc-2.6.30 Elapsed:19:55.570 Failures:6 > > 2.6.32-rc6-0000123-congestion-both Elapsed:17:29.255 Failures:2 > > 2.6.32-rc6-0001234-kswapd-quick-recheck Elapsed:14:41.068 Failures:0 > > 2.6.32-rc6-0123456-dm-crypt-unplug Elapsed:15:48.028 Failures:1 > > 2.6.32-rc6-revert-8aa7e847 Elapsed:14:48.647 Failures:0 > > > > The numbering in the kernel indicates what patches are applied. I tested > > the dm-crypt patch both in isolation and in combination with the patches > > in this series. > > > > Basically, the dm-crypt-unplug makes a small difference in performance > > overall, mostly slight gains and losses. There was one massive regression > > with the dm-crypt patch applied to 2.6.32-rc6 but at the moment, I don't > > know what that is. > > How consistent are your numbers between runs? I was trying to match > this up with your last email and things were pretty different. > The figures from the first mail were based on kernels that were not instrumented. It so happened that this run was based on an instrumented kernel to get the congestion_wait figures so the results are different. However, the results vary a lot. In some cases, it will spike just as 2.6.32-rc6-0000006-dm-crypt-unplug did. The reported figure is the average of 4 fake-gitk runs. I don't have the standard deviation handy but it's high. > > > > In general, the patch reduces the amount of time direct reclaimers are > > spending on congestion_wait. > > > > > It includes my patch from last night, along with changes to force dm to > > > unplug when its IO queues empty. > > > > > > The problem goes like this: > > > > > > Process: submit read bio > > > dm: put bio onto work queue > > > process: unplug > > > dm: work queue finds bio, does a generic_make_request > > > > > > The end result is that we miss the unplug completely. dm-crypt needs to > > > unplug for sync bios. This patch also changes it to unplug whenever the > > > queue is empty, which is far from ideal but better than missing the > > > unplugs. > > > > > > This doesn't completely fix io stalls I'm seeing with dm-crypt, but its > > > my best guess. If it works, I'll break it up and submit for real to > > > the dm people. > > > > > > > Out of curiousity, how are you measuring IO stalls? In the tests I'm doing, > > the worker processes output their progress and it should be at a steady > > rate. I considered a stall to be an excessive delay between updates which > > is a pretty indirect measure. > > I just setup a crypto disk and did dd if=/dev/zero of=/mnt/foo bs=1M > > If you watch vmstat 1, there's supposed to be a constant steam of IO to > the disk. If a whole second goes by with zero IO, we're doing something > wrong, I get a number of multi-second stalls where we are just waiting > for IO to happen. > Ok, cool. > Most of the time I was able to catch a sysrq-w for it, someone was > waiting on a read to finish. It isn't completely clear to me if the > unplugging is working properly. > The machines I'm using are now tied up doing the same tests with dm-crypt and then I need to rerun with dm-crypt with the changed patches. It'll be early next week before the machines free up again for me to investigate your patch more but initial results look promising at least. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
