Messages in this thread | | | Date | Sat, 22 Dec 2012 12:30:35 -0700 | From | David Ahern <> | Subject | Re: [GIT PULL] perf changes for v3.8 |
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On 12/17/12 3:20 AM, Gleb Natapov wrote: > Does the regression happen because of commit 20b279ddb38c. If it does I > think it is safe to revert it. KVM disables PEBS during guest entry now, so > VMs shouldn't be blowing up (they do not in my testing) and if they still > do we can disable the counter that has PEBS enabled on a guest entry too. > Yes, if user runs "perf record -e cycles:ppG" he will not know that > kernel ignored :pp modifier (with 20b279ddb38c he will get an error), but > at least old binaries will continue working and new binaries can do the > checking in userspace. >
Your patch alone was not enough. Start here: https://lkml.org/lkml/2012/7/12/3
And from your response: https://lkml.org/lkml/2012/7/12/337
"Do not run perf kvm. It does not set exclude_guest and :p and :pp is not compatible with guest profiling and should be disallowed. Again Peter's patch takes care of this."
20b279ddb38c is Peter's patch -- kernel side enforcement that exclude_guest needs to be set when using precise mode.
David
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