All of lore.kernel.org
 help / color / mirror / Atom feed
* [PATCH V2 0/5] Support metric group constraint
@ 2020-02-24 21:59 kan.liang
  2020-02-24 21:59 ` [PATCH V2 1/5] perf jevents: Support metric constraint kan.liang
                   ` (5 more replies)
  0 siblings, 6 replies; 14+ messages in thread
From: kan.liang @ 2020-02-24 21:59 UTC (permalink / raw)
  To: acme, jolsa, mingo, peterz, linux-kernel
  Cc: mark.rutland, namhyung, ravi.bangoria, yao.jin, ak, Kan Liang

From: Kan Liang <kan.liang@linux.intel.com>

Changes since V1:
- Remove global static flag violate_nmi_constraint, and add a new
  function metricgroup___watchdog_constraint_hint() for all
  watchdog constraint hints in patch 4.
  The rest of the patches are not changed.

Some metric groups, e.g. Page_Walks_Utilization, will never count when
NMI watchdog is enabled.

 $echo 1 > /proc/sys/kernel/nmi_watchdog
 $perf stat -M Page_Walks_Utilization

 Performance counter stats for 'system wide':

 <not counted>      itlb_misses.walk_pending       (0.00%)
 <not counted>      dtlb_load_misses.walk_pending  (0.00%)
 <not counted>      dtlb_store_misses.walk_pending (0.00%)
 <not counted>      ept.walk_pending               (0.00%)
 <not counted>      cycles                         (0.00%)

       2.343460588 seconds time elapsed

 Some events weren't counted. Try disabling the NMI watchdog:
        echo 0 > /proc/sys/kernel/nmi_watchdog
        perf stat ...
        echo 1 > /proc/sys/kernel/nmi_watchdog
 The events in group usually have to be from the same PMU. Try
 reorganizing the group.

A metric group is a weak group, which relies on group validation
code in the kernel to determine whether to be opened as a group or
a non-group. However, group validation code may return false-positives,
especially when NMI watchdog is enabled. (The metric group is allowed
as a group but will never be scheduled.)

The attempt to fix the group validation code has been rejected.
https://lore.kernel.org/lkml/20200117091341.GX2827@hirez.programming.kicks-ass.net/
Because we cannot accurately predict whether the group can be scheduled
as a group, only by checking current status.

This patch set provides another solution to mitigate the issue.
Add "MetricConstraint" in event list, which provides a hint for perf tool,
e.g. "MetricConstraint": "NO_NMI_WATCHDOG". Perf tool can change the
metric group to non-group (standalone metrics) if NMI watchdog is enabled.

After applying the patch,

 $echo 1 > /proc/sys/kernel/nmi_watchdog
 $perf stat -M Page_Walks_Utilization
  Splitting metric group Page_Walks_Utilization into standalone metrics.
  Try disabling the NMI watchdog to comply NO_NMI_WATCHDOG metric constraint:
        echo 0 > /proc/sys/kernel/nmi_watchdog
        perf stat ...
        echo 1 > /proc/sys/kernel/nmi_watchdog

 Performance counter stats for 'system wide':

        18,253,454      itlb_misses.walk_pending  #      0.0
                              Page_Walks_Utilization   (50.55%)
        78,051,525      dtlb_load_misses.walk_pending  (50.55%)
        29,213,063      dtlb_store_misses.walk_pending (50.55%)
                 0      ept.walk_pending               (50.55%)
     2,542,132,364      cycles                         (49.92%)

       1.037095993 seconds time elapsed

Kan Liang (5):
  perf jevents: Support metric constraint
  perf metricgroup: Factor out metricgroup__add_metric_weak_group()
  perf util: Factor out sysctl__nmi_watchdog_enabled()
  perf metricgroup: Support metric constraint
  perf vendor events: Add NO_NMI_WATCHDOG metric constraint

 .../arch/x86/cascadelakex/clx-metrics.json         |   3 +-
 .../pmu-events/arch/x86/skylake/skl-metrics.json   |   3 +-
 .../pmu-events/arch/x86/skylakex/skx-metrics.json  |   3 +-
 tools/perf/pmu-events/jevents.c                    |  19 ++--
 tools/perf/pmu-events/jevents.h                    |   2 +-
 tools/perf/pmu-events/pmu-events.h                 |   1 +
 tools/perf/util/metricgroup.c                      | 109 ++++++++++++++++-----
 tools/perf/util/stat-display.c                     |   6 +-
 tools/perf/util/util.c                             |  18 ++++
 tools/perf/util/util.h                             |   2 +
 10 files changed, 128 insertions(+), 38 deletions(-)

-- 
2.7.4


^ permalink raw reply	[flat|nested] 14+ messages in thread

end of thread, other threads:[~2020-03-19 14:12 UTC | newest]

Thread overview: 14+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2020-02-24 21:59 [PATCH V2 0/5] Support metric group constraint kan.liang
2020-02-24 21:59 ` [PATCH V2 1/5] perf jevents: Support metric constraint kan.liang
2020-03-19 14:10   ` [tip: perf/core] " tip-bot2 for Kan Liang
2020-02-24 21:59 ` [PATCH V2 2/5] perf metricgroup: Factor out metricgroup__add_metric_weak_group() kan.liang
2020-03-10 17:45   ` Arnaldo Carvalho de Melo
2020-03-19 14:10   ` [tip: perf/core] " tip-bot2 for Kan Liang
2020-02-24 21:59 ` [PATCH V2 3/5] perf util: Factor out sysctl__nmi_watchdog_enabled() kan.liang
2020-03-19 14:10   ` [tip: perf/core] " tip-bot2 for Kan Liang
2020-02-24 21:59 ` [PATCH V2 4/5] perf metricgroup: Support metric constraint kan.liang
2020-03-19 14:10   ` [tip: perf/core] " tip-bot2 for Kan Liang
2020-02-24 21:59 ` [PATCH V2 5/5] perf vendor events: Add NO_NMI_WATCHDOG " kan.liang
2020-03-19 14:10   ` [tip: perf/core] perf vendor events intel: " tip-bot2 for Kan Liang
2020-02-26 15:35 ` [PATCH V2 0/5] Support metric group constraint Jiri Olsa
2020-03-10 18:04   ` Arnaldo Carvalho de Melo

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.