This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed- trusty' to 'verification-done-trusty'.
If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you! ** Tags added: verification-needed-trusty -- 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: Fix Released Status in “linux” source package in Trusty: Fix Committed Bug description: SRU Justification: Impact: Tools that rely on diskstats may report incorrect data in certain conditions. In particular diskstats in a VM may report incorrect statistics. Fix: 0fec08b4ecfc36fd8a64432343b2964fb86d2675 ( in 3.14-rc1 ) Testcase: - Install a VM with the affected kernel - Run cat /proc/diskstats | awk '$3=="vda" { print $7/$4, $11/$8 }' - If the two values are much larger compared to the v3.14-rc1 kernel in the same VM, we have failed. For example in a failing case I see: "132.44 5458.34"; in a passing case I see: "0.19334 5.90476". -- 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
