Messages in this thread | | | Date | Thu, 26 Jul 2012 11:10:41 +0300 | From | Gleb Natapov <> | Subject | Re: [PATCH 08/11] perf tool: precise mode requires exclude_guest |
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On Thu, Jul 26, 2012 at 10:07:37AM +0200, Peter Zijlstra wrote: > On Thu, 2012-07-26 at 08:50 +0300, Gleb Natapov wrote: > > On Wed, Jul 25, 2012 at 10:35:46PM +0200, Peter Zijlstra wrote: > > > On Tue, 2012-07-24 at 18:15 +0200, Robert Richter wrote: > > > > David, > > > > > > > > On 24.07.12 08:20:19, David Ahern wrote: > > > > > On 7/23/12 12:13 PM, Arnaldo Carvalho de Melo wrote: > > > > > > Em Fri, Jul 20, 2012 at 05:25:53PM -0600, David Ahern escreveu: > > > > > >> PEBS cannot be used with guest mode. If user adds :p modifier set > > > > > >> exclude_guest as well. > > > > > > > > > > > > Is this something Intel specific? Or can someone think of an arch where > > > > > > this limitation wouldn't exist? > > > > > > > > > > Good point. So far precise_ip is used by arch/x86 only. I don't have an > > > > > AMD based server so I don't know if there is a conflict between > > > > > virtualization and IBS. Added Robert for advice. > > > > > > > > thanks for this hint. > > > > > > > > On AMD cpus precise_ip maps to IBS, which does not support hardware > > > > options as perfctrs do. Thus, following attr flags are not supported: > > > > > > > > exclude_user, exclude_kernel, exclude_host, exclude_guest > > > > > > > > Counting in guest mode is possible with IBS, but not the exclusion of > > > > a certain mode. If precise_ip counting is enabled on AMD we may not > > > > set the exclude_guest flag. > > > > > > IIRC we have SVM enter/exit hooks in kvm/perf already, we could use > > > those to implement exclude_guest for IBS. > > > > > > Now I've been trying to find the patches that introduced that, but I'm > > > failing horridly. Gleb, got us a pointer here? > > > The commit is 144d31e6, but it introduces hook that is used on VMX only. > > SVM does not need it to implement guest/host only counters since it > > has HW support for that in the PMU. > > Right, seems that has changed now that we support IBS.
Copying Joerg who wrote guest/host exclude code for AMD.
-- Gleb.
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