linux-kernel - Re: [RFC][PATCH 09/11] perf_counter: revamp syscall input ABI

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Message-ID: <18880.23662.233043.833458@drongo.ozlabs.ibm.com>
Date:	Wed, 18 Mar 2009 13:29:02 +1100
From:	Paul Mackerras <paulus@...ba.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	mingo@...e.hu, rostedt@...dmis.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 09/11] perf_counter: revamp syscall input ABI

Peter Zijlstra writes:

> The hardware/software classification in hw_event->type became a little strained
> due to the addition of tracepoint tracing.
> 
> Instead split up the field and provide a type field to explicitly specify the
> counter type, while using the event_id field to specify which event to use.
> 
> Raw counters still work as before, only the raw config now goes into raw_event.

Interesting idea, but why not also use it to express the distinction
between generic and raw hardware events ids?  Why not add a
PERF_TYPE_RAW_HARDWARE to this list:

> + * hw_event.type
> + */
> +enum perf_event_types {
> +	PERF_TYPE_HARDWARE		= 0,
> +	PERF_TYPE_SOFTWARE		= 1,
> +	PERF_TYPE_TRACEPOINT		= 2,
> +};

and get rid of the raw bit?  That way, hw_event.raw_event is unique
for every different event, whereas the way you have it, you still need
to include the raw bit to get a unique id.

Paul.
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