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perf/x86/intel: Disable userspace RDPMC usage for large PEBS

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Userspace RDPMC cannot possibly work for large PEBS, which was introduced in:

  b8241d2069 ("perf/x86/intel: Implement batched PEBS interrupt handling (large PEBS interrupt threshold)")

When the PEBS interrupt threshold is larger than one, there is no way
to get exact auto-reload times and value for userspace RDPMC.  Disable
the userspace RDPMC usage when large PEBS is enabled.

The only exception is when the PEBS interrupt threshold is 1, in which
case user-space RDPMC works well even with auto-reload events.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: acme@kernel.org
Fixes: b8241d2069 ("perf/x86/intel: Implement batched PEBS interrupt handling (large PEBS interrupt threshold)")
Link: http://lkml.kernel.org/r/1518474035-21006-6-git-send-email-kan.liang@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Kan Liang 2018-02-12 14:20:35 -08:00 committed by Ingo Molnar
parent ceb90d9e02
commit 1af22eba24
1 changed files with 2 additions and 1 deletions
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3
arch/x86/events/core.c
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@ -2117,7 +2117,8 @@ static int x86_pmu_event_init(struct perf_event *event)
event->destroy(event);
}
if (READ_ONCE(x86_pmu.attr_rdpmc))
if (READ_ONCE(x86_pmu.attr_rdpmc) &&
!(event->hw.flags & PERF_X86_EVENT_FREERUNNING))
event->hw.flags |= PERF_X86_EVENT_RDPMC_ALLOWED;
return err;