On 10/04/2012 06:14 PM, Avi Kivity wrote:
On 10/04/2012 12:56 PM, Raghavendra K T wrote:
On 10/03/2012 10:55 PM, Avi Kivity wrote:
On 10/03/2012 04:29 PM, Raghavendra K T wrote:
* Avi Kivity <avi@xxxxxxxxxx> [2012-09-27 14:03:59]:
On 09/27/2012 01:23 PM, Raghavendra K T wrote:
[...]
2) looking at the result (comparing A & C) , I do feel we have
significant in iterating over vcpus (when compared to even vmexit)
so We still would need undercommit fix sugested by PeterZ
(improving by
140%). ?
Looking only at the current runqueue? My worry is that it misses a lot
of cases. Maybe try the current runqueue first and then others.
Okay. Do you mean we can have something like
+ if (rq->nr_running == 1 && p_rq->nr_running == 1) {
+ yielded = -ESRCH;
+ goto out_irq;
+ }
in the Peter's patch ?
( I thought lot about && or || . Both seem to have their own cons ).
But that should be only when we have short term imbalance, as PeterZ
told.
I'm missing the context. What is p_rq?
p_rq is the run queue of target vcpu.
What I was trying below was to address Rik concern. Suppose
rq of source vcpu has one task, but target probably has two task,
with a eligible vcpu waiting to be scheduled.
What I mean was:
if can_yield_to_process_in_current_rq
do that
else if can_yield_to_process_in_other_rq
do that
else
return -ESRCH
I think you are saying we have to check the run queue of the
source vcpu, if we have a vcpu belonging to same VM and try yield to
that? ignoring whatever the target vcpu we received for yield_to.
Or is it that kvm_vcpu_yield_to should now check the vcpus of same vm
belonging to same run queue first. If we don't succeed, go again for
a vcpu in different runqueue.
Right. Prioritize vcpus that are cheap to yield to. But may return bad
results if all vcpus on the current runqueue are spinners, so probably
not a good idea.
Okay. 'll drop vcpu from same rq idea now.
Does it add more overhead especially in <= 1x scenario?
The current runqueue should have just our vcpu in that case, so low
overhead. But it's a bad idea due to the above scenario.
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