On Wed, Aug 20, 2014 at 03:36:03PM +0300, Alexander Shishkin wrote:
> In order to collect AUX data from an inherited event, we can redirect its
> output to parent's ring buffer if possible (they must be cpu affine). This
> patch adds set_output() to the inheritance path.
> 
> Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> ---
>  kernel/events/core.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 67f857ab56..e36478564c 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -7962,6 +7962,12 @@ inherit_event(struct perf_event *parent_event,
>  		= parent_event->overflow_handler_context;
>  
>  	/*
> +	 * Direct child's output to parent's ring buffer (if any)
> +	 */
> +	if (parent_event->cpu != -1)
> +		(void)perf_event_set_output(child_event, parent_event);
> +
> +	/*
>  	 * Precalculate sample_data sizes
>  	 */
>  	perf_event__header_size(child_event);

Uhm, nope, see perf_output_begin(), it always redirects output to parent
events.