linux-kernel - [PATCH 0/3]measure SMI cost

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Date:   Thu, 23 Mar 2017 11:25:48 -0700
From:   kan.liang@...el.com
To:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     tglx@...utronix.de, eranian@...gle.com, jolsa@...nel.org,
        ak@...ux.intel.com, Kan Liang <Kan.liang@...el.com>
Subject: [PATCH 0/3]measure SMI cost

From: Kan Liang <Kan.liang@...el.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#.

Here is an example output.

 Performance counter stats for 'sudo echo ':

SMI cycles%          SMI#
    0.1%              1

       0.010858678 seconds time elapsed

Kan Liang (3):
  perf/x86: add sysfs entry to freeze counter on SMI
  tools lib api fs: Add sysfs__write_int function
  perf stat: Add support to measure SMI cost

 arch/x86/events/core.c                 | 10 +++++++
 arch/x86/events/intel/core.c           | 48 ++++++++++++++++++++++++++++++++++
 arch/x86/events/perf_event.h           |  3 +++
 arch/x86/include/asm/msr-index.h       |  1 +
 tools/lib/api/fs/fs.c                  | 29 ++++++++++++++++++++
 tools/lib/api/fs/fs.h                  |  4 +++
 tools/perf/Documentation/perf-stat.txt |  9 +++++++
 tools/perf/builtin-stat.c              | 48 ++++++++++++++++++++++++++++++++++
 tools/perf/util/stat-shadow.c          | 33 +++++++++++++++++++++++
 tools/perf/util/stat.c                 |  2 ++
 tools/perf/util/stat.h                 |  2 ++
 11 files changed, 189 insertions(+)

-- 
2.7.4