Messages in this thread | | | Date | Mon, 24 Dec 2012 12:36:20 +0200 | From | Gleb Natapov <> | Subject | Re: [GIT PULL] perf changes for v3.8 |
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On Sun, Dec 23, 2012 at 04:17:45PM -0700, David Ahern wrote: > On 12/23/12 2:23 AM, Gleb Natapov wrote: > >>Your patch alone was not enough. Start here: > >> https://lkml.org/lkml/2012/7/12/3 > >> > >I cannot reproduce this failure. I reverted 20b279ddb38c and ran "perf > >record -e cycles:ppG" while guest was running. Admittedly I ran the test > >for a short time, but without disabling PEBS during the guest entry this > >was enough to crash a guest. > > In the beginning (without any patches) VMs crashed fairly quickly. > With your patch it took longer, but I was able to consistently crash > VMs. The thread notes server info (processor, OS) and VM versions as > well as load used for the tests -- a cpu bound process (openssl), > disk bound (dd) and network (netperf). > > It means that disabling PEBS is not enough and PMU counter should be disabled too.
> >What about forcing exclude_guest on an event that > >has precise flag set without reporting error to userspace? > > That's up to the perf maintainers -- Ingo, Peter, Arnaldo. > Personally, I don't like it since kernel side is changing the user > request. > I do not see other way to prevent guests from crashing with older perf binaries if 20b279ddb38c will be reverted.
-- Gleb.
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