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authorPeter Zijlstra <peterz@infradead.org>2014-02-11 16:01:16 +0100
committerThomas Gleixner <tglx@linutronix.de>2014-02-21 21:49:07 +0100
commitcd578abb24aa67ce468c427d3356c08ea32cf768 (patch)
tree974a97cebfc368e8bee9c1beccbbd9bda00d89ef /kernel/events
parent90ed5b0fa5eb96e1cbb34aebf6a9ed96ee1587ec (diff)
perf/x86: Warn to early_printk() in case irq_work is too slow
On Mon, Feb 10, 2014 at 08:45:16AM -0800, Dave Hansen wrote: > The reason I coded this up was that NMIs were firing off so fast that > nothing else was getting a chance to run. With this patch, at least the > printk() would come out and I'd have some idea what was going on. It will start spewing to early_printk() (which is a lot nicer to use from NMI context too) when it fails to queue the IRQ-work because its already enqueued. It does have the false-positive for when two CPUs trigger the warn concurrently, but that should be rare and some extra clutter on the early printk shouldn't be a problem. Cc: hpa@zytor.com Cc: tglx@linutronix.de Cc: dzickus@redhat.com Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: mingo@kernel.org Fixes: 6a02ad66b2c4 ("perf/x86: Push the duration-logging printk() to IRQ context") Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20140211150116.GO27965@twins.programming.kicks-ass.net Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/core.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 2067cbb378eb..45e5543e2a1e 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -243,7 +243,7 @@ static void perf_duration_warn(struct irq_work *w)
printk_ratelimited(KERN_WARNING
"perf interrupt took too long (%lld > %lld), lowering "
"kernel.perf_event_max_sample_rate to %d\n",
- avg_local_sample_len, allowed_ns,
+ avg_local_sample_len, allowed_ns >> 1,
sysctl_perf_event_sample_rate);
}
@@ -283,7 +283,12 @@ void perf_sample_event_took(u64 sample_len_ns)
update_perf_cpu_limits();
- irq_work_queue(&perf_duration_work);
+ if (!irq_work_queue(&perf_duration_work)) {
+ early_printk("perf interrupt took too long (%lld > %lld), lowering "
+ "kernel.perf_event_max_sample_rate to %d\n",
+ avg_local_sample_len, allowed_ns >> 1,
+ sysctl_perf_event_sample_rate);
+ }
}
static atomic64_t perf_event_id;