linux-kernel - Re: [PATCH] perf tools: Add 'G' and 'H' modifiers to event parsing

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Date:	Mon, 16 Apr 2012 22:10:30 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Gleb Natapov <gleb@...hat.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>, acme@...stprotocols.net,
	mingo@...hat.com, linux-kernel@...r.kernel.org, avi@...hat.com
Subject: Re: [PATCH] perf tools: Add 'G' and 'H' modifiers to event parsing

On Sun, Apr 15, 2012 at 06:23:00PM +0300, Gleb Natapov wrote:
> On Sun, Apr 15, 2012 at 05:12:22PM +0200, Peter Zijlstra wrote:
> > On Sun, 2012-04-15 at 17:59 +0300, Gleb Natapov wrote:
> > > -modifier_event [ukhp]{1,5}
> > > +modifier_event [ukhpGH]{1,5} 
> > 
> > You'd also need to increase the 5 to 7 I think, unless there's a clear
> > exclusion with some of the other flags.
> > 
> > Hmm, as it stands I think the 5 is already too low: "ukhppp" is 6.
> > 
> > We should really write this as ['u'] ['k'] ['h'] ['G'] ['H'] ['p'{1,3}],
> > not the combined thing.

you mean to match them strictly in parser, right?
because what we have now can match also stuff like 'uuu' 'kkuu' ...

So far it eludes me how to do that purely in flex and
doing this via rules in bison seems like overkill.

I'd rather keep it the way we have and do the extra check
in parse_events_modifier function.. unless someone comes up
with flex regular expression that would do that (which is
possible given my regex knowledge..) 

also we need 8 characters for it, since this seems to be
valid modifier: ukhGHppp

jirka
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