Messages in this thread | | | Date | Fri, 15 Oct 2021 12:27:58 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] perf/x86/intel: fix ICL/SPR INST_RETIRED.PREC_DIST encodings |
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On Thu, Oct 14, 2021 at 11:01:15AM -0700, Stephane Eranian wrote: > On Thu, Oct 14, 2021 at 3:09 AM Peter Zijlstra <peterz@infradead.org> wrote: > > > > On Wed, Oct 13, 2021 at 05:12:14PM -0700, Stephane Eranian wrote: > > > This patch fixes the encoding for INST_RETIRED.PREC_DIST as published by Intel > > > (download.01.org/perfmon/) for Icelake. The official encoding > > > is event code 0x00 umask 0x1, a change from Skylake where it was code 0xc0 > > > umask 0x1. > > > > > > With this patch applied it is possible to run: > > > $ perf record -a -e cpu/event=0x00,umask=0x1/pp ..... > > > > > > Whereas before this would fail. > > > > > > To avoid problems with tools which may use the old code, we maintain the old > > > encoding for Icelake. > > > > Uuuuhhhhh.. but we 'stole' event=0x00 for the fake events. There must > > not be actual hardware events there or we're in trouble. I thought Intel > > knew that, I'm sure I told them that. > > Yes, this is a pseudo event code. INST_RETIRED.PREC_DIST 0x0100 only > works on fixed counter 0 > to deliver the better sample distribution.
Ah, okay. Thanks!
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