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

Weng Meiling
2014-02-15T02:41:46Z

Hi Will,

I test kernel with this patch, the problem has be fixed. When the
event's sample_period is small, the cpu will not stall except printing
warning "oprofile: ignoring spurious overflow ignoring spurious overflow".
This is normal for unregistered event.

So would you please send a formal one? :) Thanks very much!

On 2014/2/11 23:52, Will Deacon wrote:
> 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;
>
>
>
> .
>