Messages in this thread Patch in this message | | | From | kan.liang@intel ... | Subject | [PATCH 1/1] perf/core: fix implicitly enable dynamic interrupt throttle | Date | Tue, 3 May 2016 00:26:06 -0700 |
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From: Kan Liang <kan.liang@intel.com>
This patch fixes an issue which was introduced from 'commit 91a612eea9a3 ("perf/core: Fix dynamic interrupt throttle")' The old patch unconditionally sets the perf_sample_allowed_ns value to !0. But that could trigger an issue in the following corner case. The user can disable the dynamic interrupt throttle mechanism by setting perf_cpu_time_max_percent to 0. Then they changes perf_event_max_sample_rate. For this case, the mechanism will be enabled implicitly, because perf_sample_allowed_ns becomes !0.
This patch only updates the perf_sample_allowed_ns when the dynamic interrupt throttle mechanism is enabled.
Signed-off-by: Kan Liang <kan.liang@intel.com> --- kernel/events/core.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c index 4e2ebf6..4042a3d 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -375,6 +375,14 @@ static void update_perf_cpu_limits(void) { u64 tmp = perf_sample_period_ns; + /* + * Don't update the perf_sample_allowed_ns, + * if the dynamic interrupt throttle mechanism is disabled. + */ + if (sysctl_perf_cpu_time_max_percent == 100 || + sysctl_perf_cpu_time_max_percent == 0) + return; + tmp *= sysctl_perf_cpu_time_max_percent; tmp = div_u64(tmp, 100); if (!tmp) -- 2.5.0
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