linux-kernel - Re: [PATCH 2/3 -tip] perf_counter tools: Add support to set of multiple events in one shot

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Date:	Wed, 1 Jul 2009 00:47:04 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jaswinder Singh Rajput <jaswinder@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3 -tip] perf_counter tools: Add support to set of
	multiple events in one shot


* Jaswinder Singh Rajput <jaswinder@...nel.org> wrote:

> On Tue, 2009-06-30 at 11:57 +0200, Ingo Molnar wrote:
> > * Jaswinder Singh Rajput <jaswinder@...nel.org> wrote:
> > 
> > > On Mon, 2009-06-29 at 05:57 +0200, Ingo Molnar wrote:
> > > 
> > > > The above patterns i suggested _already cover_ 'multiple events'.
> > > > 
> > > > We might define further aliases like:
> > > > 
> > > > 	all := "*"
> > > >         all-sw := "sw-*"
> > > > 
> > > > but it should all be in terms of patterns and regular 
> > > > expressions, not via some hardcoded special-case thing as your 
> > > > posted patches did.
> > > > 
> > > 
> > > It seems to me very confusing and needs lot of book-keeping and 
> > > need to rewrite whole tools/perf/util/parse-events.c because :
> > > 
> > > * means all perf_event_types :
> > > 	PERF_TYPE_HARDWARE,
> > >         PERF_TYPE_SOFTWARE,
> > >         PERF_TYPE_TRACEPOINT,
> > >         PERF_TYPE_HW_CACHE,
> > >         PERF_TYPE_RAW
> > > 
> > > hw-* means all hardware events :
> > > 	PERF_TYPE_HARDWARE,
> > >         PERF_TYPE_HW_CACHE,
> > >         PERF_TYPE_RAW
> > > 
> > > sw-* means all software events :
> > >         PERF_TYPE_SOFTWARE,
> > >         PERF_TYPE_TRACEPOINT
> > > 
> > > *cache* means all cache based events :
> > > 	PERF_COUNT_CACHE_REFERENCES, 	/* Generalized H/W */
> > > 	PERF_COUNT_CACHE_MISSES,	/* Generalized H/W */
> > >         PERF_TYPE_HW_CACHE,		/* Generalized Cache */
> > > 
> > > *write* means all write based events :
> > > 	(L1D,       WRITE,          ACCESS),
> > > 	(L1D,       WRITE,          MISS),
> > > 	(LL,        WRITE,          ACCESS),
> > > 	(LL,        WRITE,          MISS),
> > > 	(DTLB,      WRITE,          ACCESS),
> > > 	(DTLB,      WRITE,          MISS)
> > > 
> > > Please let me know why it looks complex to me, is it really 
> > > complex or I am going in wrong direction.
> > 
> > It would certainly need some reorganization of the code but the end 
> > result would be more flexible and other places could use it too, for 
> > example:
> > 
> > 	perf test -e hw-*
> > 
> > would test all (known) hardware counters.
> > 
> 
> Its true.
> 
> Can you please verify that the assumptions I made above are 
> correct.

Well, the right way to approach this is to assign each event a "full 
name" and a list of aliases/shortcuts (like we have now), and then 
do pattern matching on the full name.

So we'd have full/long event names like:

  hw-cycles
  hw-instructions
  hw-l1-cache-load-misses
  sw-minor-page-faults
  ...

to implement regex patterns over these, no event specific knowledge 
should be put into the pattern matching engine itself - it just 
blindly goes over the full names as strings.

As long as the full names are unique and structured well, this will 
work fine. The only non-trivial piece of restructuring is to make it 
easy for the pattern matching engine to iterate over all events. 
Right now they are in separate tables - perhaps they should be 
collected into a single table or so.

	Ingo
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