Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v3.14 kernel[0].
If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'. If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'. If you are unable to test the mainline kernel, for example it will not boot, please add the tag: 'kernel-unable-to-test-upstream'. Once testing of the upstream kernel is complete, please mark this bug as "Confirmed". Thanks in advance. [0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.14-rc8-trusty/ ** Changed in: linux (Ubuntu) Importance: Undecided => Medium ** Changed in: linux (Ubuntu) Status: Confirmed => Incomplete -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1297522 Title: Since Trusty /proc/diskstats shows weird values Status in “linux” package in Ubuntu: Incomplete Bug description: After upgrading some virtual machines (KVM) to Trusty I noticed really high I/O wait times, e.g. Munin graphs now show up to 200 seconds(!) read I/O wait time. See attached image. Of course real latency isn't higher than before, it's only /proc/diskstats that shows totally wrong numbers... $ cat /proc/diskstats | awk '$3=="vda" { print $7/$4, $11/$8 }' 1375.44 13825.1 From the documentation for /proc/diskstats field 4 is total number of reads completed, field 7 is the total time spent reading in milliseconds, and fields 8 and 11 are the same for writes. So above numbers are the average read and write latency in milliseconds. Same weird numbers with iowait. Note the column "await" (average time in milliseconds for I/O requests): $ iostat -dx 1 60 Linux 3.13.0-19-generic (munin) 03/25/14 _x86_64_ (2 CPU) Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util vda 2.30 16.75 72.45 24.52 572.79 778.37 27.87 1.57 620.00 450.20 1121.83 1.71 16.54 Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util vda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util vda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util vda 0.00 52.00 0.00 25.00 0.00 308.00 24.64 0.30 27813.92 0.00 27813.92 0.48 1.20 I upgraded the host system to Trusty too, however there /proc/diskstats output is normal as before. $ uname -r 3.13.0-19-generic To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1297522/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
