linux-kernel - Re: [PATCH] oprofile: check whether oprofile perf enabled in op_overflow

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Message-ID: <20140211155207.GK8693@mudshark.cambridge.arm.com>
Date:	Tue, 11 Feb 2014 15:52:07 +0000
From:	Will Deacon <will.deacon@....com>
To:	Weng Meiling <wengmeiling.weng@...wei.com>
Cc:	Robert Richter <rric@...nel.org>,
	"oprofile-list@...ts.sf.net" <oprofile-list@...ts.sf.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Li Zefan <lizefan@...wei.com>,
	"wangnan0@...wei.com" <wangnan0@...wei.com>,
	"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>,
	Huang Qiang <h.huangqiang@...wei.com>,
	"sdu.liu@...wei.com" <sdu.liu@...wei.com>
Subject: Re: [PATCH] oprofile: check whether oprofile perf enabled in
 op_overflow_handler()

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;
 
 
--
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