Messages in this thread | | | Date | Sun, 31 Aug 2008 14:09:51 -0400 | From | "Parag Warudkar" <> | Subject | Re: [REGRESSION] High, likely incorrect process cpu usage counters with kvm and 2.6.2[67] |
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On Sun, Aug 31, 2008 at 11:43 AM, Avi Kivity <avi@qumranet.com> wrote: > Running an idle Windows VM on Linux 2.6.26+ with kvm, one sees high values > for the kvm process in top (30%-70% cpu), where one would normally expect > 0%-1%. Surprisingly, the per-cpu system counters show almost 100% idle, > leading me to believe this is an accounting error and that the process does > not actually consume this much cpu.
Busted process accounting - This looks the same as http://bugzilla.kernel.org/show_bug.cgi?id=11209 . Please verify. Peter's patch in latest git stops showing "incorrect looking" CPU usage but at least the process times are still wrong, horribly. In fact the CPU usage thing in -rc5 is likely also incorrect but I need to analyze that bit a little more.
From Today's Git -
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
12961 parag 20 0 83000 8908 6628 R 0 0.1 5124415h npviewer.bin
> > I bisected this to a scheduler change, namely > > commit 3e51f33fcc7f55e6df25d15b55ed10c8b4da84cd > Author: Peter Zijlstra <a.p.zijlstra@chello.nl> > Date: Sat May 3 18:29:28 2008 +0200 > > sched: add optional support for CONFIG_HAVE_UNSTABLE_SCHED_CLOCK > this replaces the rq->clock stuff (and possibly cpu_clock()). > - architectures that have an 'imperfect' hardware clock can set > CONFIG_HAVE_UNSTABLE_SCHED_CLOCK > - the 'jiffie' window might be superfulous when we update tick_gtod > before the __update_sched_clock() call in sched_clock_tick() > - cpu_clock() might be implemented as: > sched_clock_cpu(smp_processor_id()) > if the accuracy proves good enough - how far can TSC drift in a > single jiffie when considering the filtering and idle hooks? > [ mingo@elte.hu: various fixes and cleanups ] > Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> > Signed-off-by: Ingo Molnar <mingo@elte.hu>
That patch sounds like it had open questions? Really giving this is a long standing bad regression, all the offending patches should be reverted in absence of a fix, no?
Parag
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