linux-kernel - Re: [PATCH 1/3] perf, tool: Add parser generator for events parsing

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Date:	Tue, 20 Dec 2011 11:47:50 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	acme@...hat.com, mingo@...e.hu, paulus@...ba.org,
	cjashfor@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] perf, tool: Add parser generator for events parsing

On Tue, 2011-12-20 at 11:31 +0100, Jiri Olsa wrote:
> On Fri, Dec 16, 2011 at 03:03:16PM +0100, Peter Zijlstra wrote:
> > On Fri, 2011-12-16 at 15:02 +0100, Peter Zijlstra wrote:
> > > > event_tracepoint:       PE_NAME_TP ':' PE_NAME_TP modifier
> > > > event_raw:              PE_SEP_RAW PE_VALUE modifier
> > > > event_numeric:          PE_VALUE ':' PE_VALUE modifier
> > > > event_symbolic:         PE_NAME_SYM modifier
> > > > event_generic_hw:       PE_NAME_CACHE_TYPE '-' PE_NAME_CACHE_OP_RESULT '-' PE_NAME_CACHE_OP_RESULT modifier |
> > > >                         PE_NAME_CACHE_TYPE '-' PE_NAME_CACHE_OP_RESULT modifier |
> > > >                         PE_NAME_CACHE_TYPE modifier
> > > > event_breakpoint:       PE_SEP_BP ':' PE_VALUE event_breakpoint_type modifier
> > > > event_breakpoint_type:  PE_MODIFIER_BPTYPE | empty
> > > > modifier:               PE_MODIFIER_EVENT | empty
> > > 
> > > This isn't complete, we need means of specifying
> > > perf_event_attr::config[12] when specifying a raw event. 
> > 
> > Also, it might make sense to think about how to specify sysfs events
> > (which don't exist yet).
> 
> any idea/details/specifics how they might look like? ;)

The current idea is that they'd live in a place like:

  /sys/bus/event_source/devices/$pmu/events/$event

and when you read them they contain a full event_raw style string so you
could do things like:

  perf record -e `cat $sysfsfile` or so

(or maybe without the 'r' prefix).

The idea was to have some $pmu:$event like syntax, but seeing that ':'
is already used quite a lot, there's maybe a more suitable separator.
Maybe '/' would do, yielding things like cpu/instructions.

Then again, it might make sense to restructure the syntax without
considerations for the status quo and see if we can come up with
something a little more consistent, the above event_* things are quite a
hodge podge, syntax wise.

While I appreciate that they are the result of organic growth, it
doesn't mean we shouldn't try and restructure stuff once in a while when
it makes sense.
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