On 10/05/2010 01:00 PM, rukhsana ansari wrote:
Hi,
W.r.t:
> Note that this is a tradeoff. If an idle core is available and the
> scheduler places the iothread on that core, then the heavyweight exit is
> replaced by a lightweight exit + IPI. If the iothread is co-located with
> the vcpu, then we'll take a heavyweight exit in any case.
>
Q: Does the kvm kernel code check for such a condition and take a
heavyweight exit?
No. The heavyweight exit is caused by a context switch (partial) or
return to userspace (full).
> The first case is very likely if the host cpu is undercommitted and there is
> heavy I/O activity. This is a typical subsystem benchmark scenario (as
> opposed to a system benchmark like specvirt). My feeling is that total
> system throughput will be decreased unless the scheduler is clever enough to
> place the iothread and vcpu on the same host cpu when the system is
> overcommitted.
>
>
Q: Sorry if the answer is obvious here.
If the heavyweight exit is taken when both threads are assigned to the
same core, how will the system throughput increase?
Co-locating threads on the same core reduces cross-core traffic.
--
error compiling committee.c: too many arguments to function
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