linux-kernel - Re: [RFC][PATCH v2 11/11] perf top: demo of how to use the sysfs interface

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Date:	Wed, 19 May 2010 11:18:23 -0700
From:	Corey Ashford <cjashfor@...ux.vnet.ibm.com>
To:	Lin Ming <ming.m.lin@...el.com>
CC:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	"eranian@...il.com" <eranian@...il.com>,
	"Gary.Mohr@...l.com" <Gary.Mohr@...l.com>,
	"arjan@...ux.intel.com" <arjan@...ux.intel.com>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	Paul Mackerras <paulus@...ba.org>,
	"David S. Miller" <davem@...emloft.net>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Will Deacon <will.deacon@....com>,
	Maynard Johnson <mpjohn@...ibm.com>,
	Carl Love <carll@...ibm.com>,
	"greg@...ah.com" <greg@...ah.com>,
	Kay Sievers <kay.sievers@...y.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH v2 11/11] perf top: demo of how to use the sysfs
 interface



On 5/18/2010 6:49 PM, Lin Ming wrote:
> Just a temporary patch to show how to use the pmu sysfs interface...
> 
> Signed-off-by: Lin Ming <ming.m.lin@...el.com>
> ---
>  tools/perf/builtin-top.c |   13 +++++++++++++
>  1 files changed, 13 insertions(+), 0 deletions(-)
> 
> diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
> index adc179d..eaa9405 100644
> --- a/tools/perf/builtin-top.c
> +++ b/tools/perf/builtin-top.c
> @@ -1206,6 +1206,7 @@ static void start_counter(int i, int counter)
>  	struct perf_event_attr *attr;
>  	int cpu;
>  	int thread_index;
> +	int sys_fd;
> 
>  	cpu = profile_cpu;
>  	if (target_tid == -1 && profile_cpu == -1)
> @@ -1226,9 +1227,21 @@ static void start_counter(int i, int counter)
> 
>  	for (thread_index = 0; thread_index < thread_num; thread_index++) {
>  try_again:
> +		/*
> +		 * This is just an ugly demo of how to use the sysfs interface.
> +		 * You can also parse the <event-name> and open sys file as,
> +		 * sys_fd = open("/sys/devices/system/cpu/events/<event-name>/event_source/id", O_RDONLY);
> +		 */

In this above case, does this sys_fd also specify the event I am going to open, in addition to its event source?  I'd assume not since event_source is a symlink to /sys/devices/system/cpu/event_source (right?)

How do I specify the exact event id via the sysfs interface?

Thanks,

- Corey

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