linux-kernel - Re: [RFC] perf/x86/intel: Account interrupts for PEBS errors

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Date:   Wed, 14 Dec 2016 19:07:30 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Andi Kleen <andi@...stfloor.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Vince Weaver <vince@...ter.net>, Ingo Molnar <mingo@...nel.org>
Subject: Re: [RFC] perf/x86/intel: Account interrupts for PEBS errors

On Wed, Dec 14, 2016 at 05:50:36PM +0100, Jiri Olsa wrote:
> 
> I also fail to reproduce on other than snb_x (model 45) server

reproduces on my ivb-ep as well model 62.

> thoughts?

cute find :-)

> +++ b/arch/x86/events/intel/ds.c
> @@ -1389,9 +1389,13 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs)
>  			continue;
>  
>  		/* log dropped samples number */
> -		if (error[bit])
> +		if (error[bit]) {
>  			perf_log_lost_samples(event, error[bit]);
>  
> +			if (perf_event_account_interrupt(event, 1))

Seems a bit daft to expose the .throttle argument, since that would be
the only point of calling this.




> +static int __perf_event_overflow(struct perf_event *event,
> +				   int throttle, struct perf_sample_data *data,
> +				   struct pt_regs *regs)
> +{
> +	int events = atomic_read(&event->event_limit);
> +	struct hw_perf_event *hwc = &event->hw;
> +	int ret = 0;
> +
> +	/*
> +	 * Non-sampling counters might still use the PMI to fold short
> +	 * hardware counters, ignore those.
> +	 */
> +	if (unlikely(!is_sampling_event(event)))
> +		return 0;
> +
> +	ret = perf_event_account_interrupt(event, throttle);
> +
>  	if (event->attr.freq) {
>  		u64 now = perf_clock();
>  		s64 delta = now - hwc->freq_time_stamp;

Arguably, everything in __perf_event_overflow() except for calling of
->overflow_handler() should be done I think.