On Wed, 20 Jun 2012 01:50:50 +0530 Raghavendra K T <[email protected]> wrote:
> > In ple handler code, last_boosted_vcpu (lbv) variable is > serving as reference point to start when we enter. > Also statistical analysis (below) is showing lbv is not very well > distributed with current approach. You are the second person to spot this bug today (yes, today). Due to time zones, the first person has not had a chance yet to test the patch below, which might fix the issue... Please let me know how it goes. ====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 <[email protected]> --- 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) -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
