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

[Corey Ashford <cjashfor@linux.vnet.ibm.com>]

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@intel.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