Re: [PATCH] kvm: handle last_boosted_vcpu = 0 case

[Rik van Riel]

On 06/20/2012 04:12 PM, Raghavendra K T wrote:
> On 06/20/2012 02:21 AM, Rik van Riel wrote:

> > Please let me know how it goes.
>
> Yes, have got result today, too tired to summarize. got better
> performance result too. will come back again tomorrow morning.
> have to post, randomized start point patch also, which I discussed to
> know the opinion.

The other person's problem has also gone away with this
patch.

Avi, could I convince you to apply this obvious bugfix
to kvm.git? :)

> > ====8<====
> >
> > If last_boosted_vcpu == 0, then we fall through all test cases and
> > may end up with all VCPUs pouncing on vcpu 0. With a large enough
> > guest, this can result in enormous runqueue lock contention, which
> > can prevent vcpu0 from running, leading to a livelock.
> >
> > Changing< to<= makes sure we properly handle that case.

> > Signed-off-by: Rik van Riel<riel@xxxxxxxxxx>
> > ---
> > virt/kvm/kvm_main.c | 2 +-
> > 1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index 7e14068..1da542b 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -1586,7 +1586,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
> > */
> > for (pass = 0; pass< 2&& !yielded; pass++) {
> > kvm_for_each_vcpu(i, vcpu, kvm) {
> > - if (!pass&& i< last_boosted_vcpu) {
> > + if (!pass&& i<= last_boosted_vcpu) {
> > i = last_boosted_vcpu;
> > continue;
> > } else if (pass&& i> last_boosted_vcpu)


--
All rights reversed
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/