linux-kernel - Re: [RESEND PATCH V2 3/4] perf/x86/intel: drain PEBS buffer in event read

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Date:   Wed, 10 Jan 2018 11:39:29 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     kan.liang@...el.com
Cc:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de,
        eranian@...gle.com, ak@...ux.intel.com,
        Kan Liang <kan.liang@...ux.intel.com>
Subject: Re: [RESEND PATCH V2 3/4] perf/x86/intel: drain PEBS buffer in event
 read

On Mon, Jan 08, 2018 at 07:15:15AM -0800, kan.liang@...el.com wrote:
> From: Kan Liang <kan.liang@...ux.intel.com>
> 
> When the PEBS interrupt threshold is larger than one, there is no way to
> get exact auto-reload times and value needed for event update unless
> flush the PEBS buffer.
> 
> Drain the PEBS buffer in event read when large PEBS is enabled.
> 
> For the threshold is one, even auto-reload is enabled, it doesn't need
> to be specially handled. Because auto-reload is only effect when event
> overflow. There is no overflow in event read.
> 
> Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
> ---
>  arch/x86/events/intel/core.c |  9 +++++++++
>  arch/x86/events/intel/ds.c   | 10 ++++++++++
>  arch/x86/events/perf_event.h |  2 ++
>  3 files changed, 21 insertions(+)
> 
> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
> index 09c26a4..bdc35f8 100644
> --- a/arch/x86/events/intel/core.c
> +++ b/arch/x86/events/intel/core.c
> @@ -2060,6 +2060,14 @@ static void intel_pmu_del_event(struct perf_event *event)
>  		intel_pmu_pebs_del(event);
>  }
>  
> +static void intel_pmu_read_event(struct perf_event *event)
> +{
> +	if (event->attr.precise_ip)
> +		return intel_pmu_pebs_read(event);

check for (event->hw.flags & PERF_X86_EVENT_AUTO_RELOAD)
would be more accurate?

jirka