On Wed, Aug 20, 2014 at 03:36:16PM +0300, Alexander Shishkin wrote:
> AUX data can be used to annotate other perf events by including it in
> sample records when PERF_SAMPLE_AUX flag is set. In this case, a kernel
> counter is created for each such event and trace data is retrieved
> from it and stored in the perf data stream.
>
> To this end, new attribute fields are added:
> * aux_sample_type: specify PMU on which the AUX data generating event
> is created;
> * aux_sample_config: event config (maps to attribute's config field),
> * aux_sample_size: size of the sample to be written.
>
> This kernel counter is configured similarly to its "main" event with
> regards to filtering (exclude_{hv,idle,user,kernel}) and enabled state
> (disabled, enable_on_exec) to make sure that we don't get out of context
> AUX traces.WHY? Why would we want to do this? This doesn't tell me why I should want this or even consider it. Convince me I want to read the patch.
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