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[0/1] KVM: selftests: pmu_counters_test: increase robustness of LLC cache misses

Message ID 20240621204305.1730677-1-mlevitsk@redhat.com
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Series KVM: selftests: pmu_counters_test: increase robustness of LLC cache misses | expand

Message

Maxim Levitsky June 21, 2024, 8:43 p.m. UTC 
Recent CI failures brought my attention to the fact that pmu_counters_test
sometimes fails because it doesn't get any LLC cache misses.

It apparently happens because CLFLUSH can race with CPU prediction.

To attempt to fix this, implement a more aggressive cache flushing - now it is flushed
on each iteration of the measured loop which should at least reduce by order
of magnitude the chance of this happening.

This patch survived more that a day of running in a loop on a Comet Lake machine,
where the test used to fail after about 10-20 minites.

Best regards,
	Maxim Levitsky

Maxim Levitsky (1):
  KVM: selftests: pmu_counters_test: increase robustness of LLC cache
    misses

 .../selftests/kvm/x86_64/pmu_counters_test.c  | 20 +++++++++----------
 1 file changed, 9 insertions(+), 11 deletions(-)