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.
Signed-off-by: Laurent Vivier <Laurent.Vivier@xxxxxxxx>
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"Software is hard" - Donald Knuth
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