https://bugzilla.novell.com/show_bug.cgi?id=820175 https://bugzilla.novell.com/show_bug.cgi?id=820175#c0 Summary: very regular freezes due to I/O spikes on btrfs filesystems Classification: openSUSE Product: openSUSE 12.3 Version: Final Platform: Other OS/Version: Other Status: NEW Severity: Major Priority: P5 - None Component: Kernel AssignedTo: kernel-maintainers@forge.provo.novell.com ReportedBy: aspiers@suse.com QAContact: qa-bugs@suse.de Found By: Development Blocker: --- As described on https://mailman.suse.de/mailman/private/research/2013-April/002912.html I am using btrfs on LVM on md (RAID1) for / and /home on my 12.3 desktop and am experiencing regular freezes each lasting for between a few seconds and a few minutes. During each freeze, gkrellm shows I/O spikes of typically at least 1MB/s for sda and sdb, and the whole desktop becomes unusable: not just operations which require disk I/O, but even typing characters into an existing urxvt becomes impossible, any audio/video streaming from the internet will stutter or pause etc. Quite regularly I will save a small shell script to disk and it takes so long to finish the write (10 seconds or more) that I encounter a "text file busy" error when trying to execute the resulting script. I strongly suspect that this is related to btrfs fragmentation - the first issue listed on this page: https://btrfs.wiki.kernel.org/index.php/Gotchas describes symptoms very similar to what I am seeing, e.g. btrfs-endio-wri appearing at the top of iotop. However, I have had the btrfs filesystems mounted with autodefrag for a long time, ever since I discovered the above page, and I have also run "btrfs filesystem defrag" on both / and /home several times. Performance was a bit better (but still really not great) for a while when /home was at 90% capacity or less, but now it is at 92% and I am seeing the freezes multiple times in most hours. A long time ago I removed all snapshots and disabled snapper to ensure it wasn't related to this. Current kernel is 3.7.10-10-desktop. This is clearly a severe bug as it makes the whole machine unusable for a significant amount of time each day. I don't know whether it's because most people don't use btrfs for /home and/or the root fs, or something else peculiar to my hardware or setup. I typically have at least one or more KVM virtual machines running but they live on a separate ext4 partition which is at 59% capacity (50GB free) and are sitting idle 99% of the time. In contrast the freezes either happen spontaneously or are triggered by I/O on /home or the root fs. Even if it's a btrfs bug, I don't understand how it apparently blocks every single running process on a 4-core Intel i7 box with 16GB of RAM, the majority of which is not used? So it seems to be a pretty bad corner case. I would be delighted to help a btrfs / kernel expert debug it! I can arrange ssh access if necessary. -- Configure bugmail: https://bugzilla.novell.com/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug.