linux-kernel - Re: [PATCH v5 1/4] tools/perf: support parsing parameterized events

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Date:	Thu, 4 Dec 2014 13:44:22 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Michael Ellerman <michaele@....ibm.com>,
	Paul Mackerras <paulus@...ba.org>, dev@...yps.com,
	peterz@...radead.org, hbabu@...ibm.com,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v5 1/4] tools/perf: support parsing parameterized events

On Tue, Dec 02, 2014 at 06:09:35PM -0800, Sukadev Bhattiprolu wrote:
> From: Cody P Schafer <cody@...ux.vnet.ibm.com>
> 
> Enable event specification like:
> 
> 	pmu/event_name,param1=0x1,param2=0x4/
> 
> Assuming that
> 
> 	/sys/bus/event_source/devices/pmu/events/event_name
> 
> Contains something like
> 
> 	param2=$foo,bar=1,param1=$baz

oops.. sorry to be PITA on this one.. I might have missed something
in the previous discussion but I guess I might have finally some
opinion on this ;-)

here's how I think your patchset works:

in /sys/bus/event_source/devices/pmu/events/event_name you can actually have:

   param2=foo,bar=1,param1=baz

notice no '$', thats what you add later in 'perf list' output, right?

Moreover it actually does not matter whats in value 'param2=HERE',
because it's not used in the config code at all apart from the
'perf list' display processing.

So when we discussed the '$' name way, I thought it'd be like:

in /sys/bus/event_source/devices/pmu/events/event_name you have:
  param2=$foo,bar=1,param1=$baz

and on command line you'd use:
  pmu/event_name,foo=0x1,bar=0x4/

to assign directly to the $var, which would justify the $var
syntax I think..

anyway we could assign directly to the param term name as you do,
but I think we just need to mark the term as parametrized, like:

in /sys/bus/event_source/devices/pmu/events/event_name you have:
  param2=?,bar=1,param1=?

and on command line you'd use:
  pmu/event_name,param2=0x1,param1=0x4/

while the config code would check that the param substitution is
done only for terms with '?' in value, like 'param2=?' and not
for all PARSE_EVENTS__TERM_TYPE_STR type terms (as of now)

thanks,
jirka
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