linux-kernel - Re: [PATCH v8 14/14] perf: add ITRACE_START record to indicate that tracing has started

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Message-ID: <20150109141248.GO3337@twins.programming.kicks-ass.net>
Date:	Fri, 9 Jan 2015 15:12:48 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Robert Richter <rric@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Andi Kleen <ak@...ux.intel.com>, kan.liang@...el.com,
	adrian.hunter@...el.com, markus.t.metzger@...el.com,
	mathieu.poirier@...aro.org, acme@...radead.org
Subject: Re: [PATCH v8 14/14] perf: add ITRACE_START record to indicate that
 tracing has started

On Fri, Nov 14, 2014 at 03:43:47PM +0200, Alexander Shishkin wrote:
> +++ b/include/uapi/linux/perf_event.h
> @@ -750,6 +750,17 @@ enum perf_event_type {
>  	 */
>  	PERF_RECORD_AUX				= 11,
>  
> +	/*
> +	 * Indicates that instruction trace has started
> +	 *
> +	 * struct {
> +	 *	struct perf_event_header	header;
> +	 *	u32				pid;
> +	 *	u32				tid;

The below function suggests we should have:

		struct sample_id		sample_id;

> +	 * };
> +	 */
> +	PERF_RECORD_ITRACE_START		= 12,
> +
>  	PERF_RECORD_MAX,			/* non-ABI */
>  };

> +static void perf_log_itrace_start(struct perf_event *event)
> +{
> +	struct perf_output_handle handle;
> +	struct perf_sample_data sample;
> +	struct perf_aux_event {
> +		struct perf_event_header        header;
> +		u32				pid;
> +		u32				tid;
> +	} rec;
> +	int ret;
> +
> +	if (event->parent)
> +		event = event->parent;
> +
> +	if (!(event->pmu->capabilities & PERF_PMU_CAP_ITRACE) ||
> +	    event->hw.itrace_started)
> +		return;
> +
> +	event->hw.itrace_started = 1;
> +
> +	rec.header.type	= PERF_RECORD_ITRACE_START;
> +	rec.header.misc	= 0;
> +	rec.header.size	= sizeof(rec);
> +	rec.pid	= perf_event_pid(event, current);
> +	rec.tid	= perf_event_tid(event, current);
> +
> +	perf_event_header__init_id(&rec.header, &sample, event);
> +	ret = perf_output_begin(&handle, event, rec.header.size);
> +
> +	if (ret)
> +		return;
> +
> +	perf_output_put(&handle, rec);
> +	perf_event__output_id_sample(event, &handle, &sample);
> +
> +	perf_output_end(&handle);
> +}
--
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