linux-kernel - RE: [PATCH 2/5] perf/x86: add PERF_SAMPLE_SKID

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Message-ID: <37D7C6CF3E00A74B8858931C1DB2F0775370DC74@SHSMSX103.ccr.corp.intel.com>
Date:   Thu, 15 Jun 2017 15:40:07 +0000
From:   "Liang, Kan" <kan.liang@...el.com>
To:     Stephane Eranian <eranian@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "acme@...hat.com" <acme@...hat.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "mingo@...e.hu" <mingo@...e.hu>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "jolsa@...hat.com" <jolsa@...hat.com>
Subject: RE: [PATCH 2/5] perf/x86: add PERF_SAMPLE_SKID_IP support for X86
 PEBS



> This patch adds support for SKID_IP to Intel x86 processors in PEBS mode. In
> that case, the off-by-1 IP from PEBS is returned in the SKID_IP field.

It looks we can only get different skid_ip and ip with :pp event (attr.precise = 2).
With the :p event (attr.precise = 1), the skid_ip and ip are the same. Right?

Thanks,
Kan

> 
> Signed-off-by: Stephane Eranian <eranian@...gle.com>
> ---
>  arch/x86/events/intel/ds.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c index
> c6d23ffe422d..ee17de5d6b8d 100644
> --- a/arch/x86/events/intel/ds.c
> +++ b/arch/x86/events/intel/ds.c
> @@ -1169,6 +1169,13 @@ static void setup_pebs_sample_data(struct
> perf_event *event,
>  	    x86_pmu.intel_cap.pebs_format >= 1)
>  		data->addr = pebs->dla;
> 
> +	/*
> +	 * unmodified, skid IP which is guaranteed to be the next
> +	 * dyanmic instruction
> +	 */
> +	if (sample_type & PERF_SAMPLE_SKID_IP)
> +		data->skid_ip = pebs->ip;
> +
>  	if (x86_pmu.intel_cap.pebs_format >= 2) {
>  		/* Only set the TSX weight when no memory weight. */
>  		if ((sample_type & PERF_SAMPLE_WEIGHT) && !fll)
> --
> 2.13.1.518.g3df882009-goog