diff options
| author | Kan Liang <kan.liang@intel.com> | 2016-05-03 00:26:06 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-06-03 09:40:16 +0200 |
| commit | ab7fdefba68f66c8523571c3b3a940635d781824 (patch) | |
| tree | 36c28f0292b06116e6ed4d3cdd35dfc58b173492 | |
| parent | aab5b71ef2b5c62323b9abe397e2db57b18e1f78 (diff) | |
perf/core: Fix implicitly enable dynamic interrupt throttle
This patch fixes an issue which was introduced by commit:
91a612eea9a3 ("perf/core: Fix dynamic interrupt throttle")
... which commit unconditionally sets the perf_sample_allowed_ns value
to !0. But that could trigger a bug 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 change perf_event_max_sample_rate.
For this case, the mechanism will be enabled implicitly, because
perf_sample_allowed_ns becomes !0 - which is not what we want.
This patch only updates perf_sample_allowed_ns when the dynamic
interrupt throttle mechanism is enabled.
Signed-off-by: Kan Liang <kan.liang@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
Link: http://lkml.kernel.org/r/1462260366-3160-1-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | kernel/events/core.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index f54454ea5f31..f94f164b5054 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -397,6 +397,13 @@ int perf_proc_update_handler(struct ctl_table *table, int write, if (ret || !write) return ret; + /* + * If throttling is disabled don't allow the write: + */ + if (sysctl_perf_cpu_time_max_percent == 100 || + sysctl_perf_cpu_time_max_percent == 0) + return -EINVAL; + max_samples_per_tick = DIV_ROUND_UP(sysctl_perf_event_sample_rate, HZ); perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate; update_perf_cpu_limits(); |