RE: [PATCH 0/3]measure SMI cost

From	"Liang, Kan" <kan.liang@intel.com>
Newsgroups	linux.kernel
Subject	RE: [PATCH 0/3]measure SMI cost
Date	2017-04-01 03:50 +0200
Message-ID	<trgkV-4cy-5@gated-at.bofh.it> (permalink)
References	<tofOp-6a9-23@gated-at.bofh.it> <trcKm-1KJ-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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> On Thu, Mar 23, 2017 at 11:25 AM,  <kan.liang@intel.com> wrote:
> > From: Kan Liang <Kan.liang@intel.com>
> >
> > Currently, there is no way to measure the time cost in System
> > management mode (SMM) by perf.
> >
> > Intel perfmon supports FREEZE_WHILE_SMM bit in IA32_DEBUGCTL. Once
> it
> > sets, the PMU core counters will freeze on SMI handler. But it will
> > not have an effect on free running counters. E.g. APERF counter.
> > The cost of SMI can be measured by (aperf - cycles).
> >
> > A new sysfs entry /sys/device/cpu/freeze_on_smi is introduced to set
> > FREEZE_WHILE_SMM bit in IA32_DEBUGCTL.
> >
> > A new --smi-cost mode in perf stat is implemented to measure the SMI
> > cost by calculating cycles and aperf results. In practice, the
> > percentages of SMI cycles should be more useful than absolute value.
> > So the output will be the percentage of SMI cycles and SMI#.
> >
> You are talking about the percentage of what cycles?
> Wallclock, unhalted_ref_cycles, unhalted_core_cycles?

Unhalted core cycles.

Thanks,
Kan

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Re: [PATCH 0/3]measure SMI cost Stephane Eranian <eranian@google.com> - 2017-04-01 00:00 +0200
  RE: [PATCH 0/3]measure SMI cost "Liang, Kan" <kan.liang@intel.com> - 2017-04-01 03:50 +0200

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