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    SubjectRe: [PATCH 0/4] Virtual Machine Time Accounting
    On Tue, 04 Aug 2009 16:16:38 +0200
    Peter Zijlstra <> wrote:

    > These patches never seem to have made it onto LKML?!
    > On Mon, 2007-08-20 at 15:13 +0200, Laurent Vivier wrote:
    > > The aim of these four patches is to introduce Virtual Machine time accounting.
    > >
    > > _Ingo_, as these patches modify files of the scheduler, could you have a look to
    > > them, please ?
    > >
    > > [PATCH 1/4] as recent CPUs introduce a third running state, after "user" and
    > > "system", we need a new field, "guest", in cpustat to store the time used by
    > > the CPU to run virtual CPU. Modify /proc/stat to display this new field.
    > >
    > > [PATCH 2/4] like for cpustat, introduce the "gtime" (guest time of the task) and
    > > "cgtime" (guest time of the task children) fields for the
    > > tasks. Modify signal_struct and task_struct. Modify /proc/<pid>/stat to display
    > > these new fields.
    > >
    > > [PATCH 3/4] modify account_system_time() to add cputime to cpustat->guest if we
    > > are running a VCPU. We add this cputime to cpustat->user instead of
    > > cpustat->system because this part of KVM code is in fact user code although it
    > > is executed in the kernel. We duplicate VCPU time between guest and user to
    > > allow an unmodified "top(1)" to display correct value. A modified "top(1)" is
    > > able to display good cpu user time and cpu guest time by subtracting cpu guest
    > > time from cpu user time. Update "gtime" and "cgtime" in signal_struct and
    > > task_struct accordingly.
    > >
    > > [PATCH 4/4] Modify KVM to update guest time accounting.
    > Isn't this exactly what CONFIG_VIRT_CPU_ACCOUNTING is about?

    Not really, CONFIG_VIRT_CPU_ACCOUNT is a mechanism to sort out the
    steal time in the >guest< and to increase the precision of the cpu
    accounting values in general. The patches from Laurent improve the
    code in the >host< that sorts out guest time vs. system time. The
    patches do make sense to me.

    blue skies,

    "Reality continues to ruin my life." - Calvin.

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