Messages in this thread | | | Date | Wed, 28 May 2014 17:36:33 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC PATCH 5/7] perf, x86: use the PEBS auto reload mechanism when possible |
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On Wed, May 28, 2014 at 07:46:43AM -0700, Andi Kleen wrote: > On Wed, May 28, 2014 at 09:59:37AM +0200, Peter Zijlstra wrote: > > On Wed, May 28, 2014 at 02:18:08PM +0800, Yan, Zheng wrote: > > > When a fixed period is specified, this patch make perf use the PEBS > > > auto reload mechanism. This makes normal profiling faster, because > > > it avoids one costly MSR write in the PMI handler. > > > > > > > You can't do this unconditionally. Like I think you mention in the next > > patch, we need the PMI to fix up lots of cases. > > There are two cases: > > (1) Fixed period specified with PEBS. > The PMI still runs with threshold=1, but we can use the PEBS > auto-reload mechanism to automatically rewrite the counter which is > faster. > > (2) Free running mode with more constraints > > This is case (1)
Sounds like something that should've been made clear in the Changelog. [unhandled content-type:application/pgp-signature] | |