linux-kernel - Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering

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Date:	Fri, 11 Dec 2015 23:39:30 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	vince@...ter.net, eranian@...gle.com,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Mathieu Poirier <mathieu.poirier@...aro.org>
Subject: Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering

On Fri, Dec 11, 2015 at 07:13:10PM +0200, Alexander Shishkin wrote:
> Peter Zijlstra <peterz@...radead.org> writes:
> > On second thought; we should not inherit the filters at all.
> >
> > We should always use event->parent (if exists) for filters. Otherwise
> > inherited events will get different filters if you change the filter
> > after clone.
> 
> But children will have different mappings,

_can_ have.

> so the actual filter
> configurations will still differ between parents and children. I guess I
> could split the filter in two parts: one that's defined by the user and
> one that we calculated from vma addresses, that we later program into
> hardware.

/me confused, isn't that what you already do?

In any case, since inherited counters are uncontrollable (they have no
filedesc of their own) and you cannot a priory tell what a child will go
do, let alone a child of a child. It really makes no sense to have
different filters on different parts of the inherited tree.

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