Re: [PATCH] oprofile: check whether oprofile perf enabled in op_overflow_handler()

Will Deacon
2014-02-11T15:52:31Z

On Tue, Feb 11, 2014 at 04:33:51AM +0000, Weng Meiling wrote:
> Hi Will,

Hello,

> >>> how userland can be notified about throttling. Throttling could be
> >>> worth for operf too, not only for the oprofile kernel driver.
> >>>
> >
> >>> From a quick look it seems there is also code in x86 that dynamically
> >>> adjusts the rate which might be worth being implemented for ARM too.
> >>
> >> Are you referring to the perf_sample_event_took callback? If so, that
> >> certainly looks worth persuing. I'll stick it on my list, thanks!
> >>
>
> Is there any progress on this work? Because this is important for me.
> Sorry for trouble you.

Oops, I totally forgot about this. Does the below patch work for you?

Will

--->8

diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index 361a1aaee7c8..a6bc431cde70 100644
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -302,6 +302,8 @@ static irqreturn_t armpmu_dispatch_irq(int irq, void *dev)
struct arm_pmu *armpmu;
struct platform_device *plat_device;
struct arm_pmu_platdata *plat;
+ int ret;
+ u64 start_clock, finish_clock;

if (irq_is_percpu(irq))
dev = *(void **)dev;
@@ -309,10 +311,15 @@ static irqreturn_t armpmu_dispatch_irq(int irq, void *dev)
plat_device = armpmu->plat_device;
plat = dev_get_platdata(&plat_device->dev);

+ start_clock = sched_clock();
if (plat && plat->handle_irq)
- return plat->handle_irq(irq, dev, armpmu->handle_irq);
+ ret = plat->handle_irq(irq, dev, armpmu->handle_irq);
else
- return armpmu->handle_irq(irq, dev);
+ ret = armpmu->handle_irq(irq, dev);
+ finish_clock = sched_clock();
+
+ perf_sample_event_took(finish_clock - start_clock);
+ return ret;
}

static void
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 56003c6edfd3..6fcc293d77a4 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -237,6 +237,8 @@ void perf_sample_event_took(u64 sample_len_ns)
u64 local_samples_len;
u64 allowed_ns = ACCESS_ONCE(perf_sample_allowed_ns);

+ pr_info("perf_sample_event_took(%llu ns)\n", sample_len_ns);
+
if (allowed_ns == 0)
return;