On Tue, Jun 19, 2012 at 04:51:04PM -0400, Rik van Riel wrote: > On Wed, 20 Jun 2012 01:50:50 +0530 > Raghavendra K T <raghavendra...@linux.vnet.ibm.com> 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 <r...@redhat.com>
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