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

[Weng Meiling <wengmeiling.weng@huawei.com>]

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;
>  
>  
> 
> .
>