Re: [kvm-devel] [PATCH 0/2][KVM] guest time accounting

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Laurent Vivier wrote:
The aim of these two patches is to measure the CPU time used by a virtual
machine. All comments are welcome... I'm not sure it's the good way to do that.

[PATCH 1/2] introduce 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 2/2] 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.

[copying Ingo and Rusty]

The patches look good.  A couple of comments:

- perhaps the new fields should be guarded by a #ifdef CONFIG_HYPERVISOR (selected by CONFIG_KVM)? that way the (minor) additional overhead is only incurred if it can possibly be used. I imagine that our canine cousin will want to use this as well.

- I think that there is per-task accounting of user time and system time; that should be extended as well.



--
error compiling committee.c: too many arguments to function

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