On 12/01/2017 03:25 PM, Matt McKinnon wrote: > > Is there any way to figure out what exactly btrfs-transacti is chugging > on? I have a few file systems that seem to get wedged for days on end > with this process pegged around 100%. I've stopped all snapshots, made > sure no quotas were enabled, turned on autodefrag in the mount options, > tried manual defragging, kernel upgrades, yet still this brings my > system to a crawl. > > Network I/O to the system seems very tiny. The only I/O I see to the > disk is btrfs-transacti writing a couple M/s. > > # time touch foo > > real 2m54.303s > user 0m0.000s > sys 0m0.002s > > # uname -r > 4.12.8-custom > > # btrfs --version > btrfs-progs v4.13.3 > > Yes, I know I'm a bit behind there...
One of the simple things you can do is watch the stack traces of the kernel thread. watch 'cat /proc/<pid>/stack' where <pid> is the pid of the btrfs-transaction process. In there, you will see a pattern of reoccuring things, like, it's searching for free space, it's writing out free space cache, or other things. Correlate this with the disk write traffic and see if we get a step further. -- Hans van Kranenburg -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
