linux-kernel - Re: [GIT PULL v2] bkl tracepoints + filter regex support

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Message-ID: <20090925091229.GB4686@nowhere>
Date:	Fri, 25 Sep 2009 11:12:30 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Tom Zanussi <tzanussi@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Li Zefan <lizf@...fujitsu.com>
Subject: Re: [GIT PULL v2] bkl tracepoints + filter regex support

On Fri, Sep 25, 2009 at 10:19:52AM +0200, Peter Zijlstra wrote:
> On Thu, 2009-09-24 at 23:36 +0200, Frederic Weisbecker wrote:
> 
> > > Remember, there are no second chances for the filter syntax anymore.
> > 
> > 
> > But well, it's not yet an ABI. It's still a baby, although powerful
> > for filtering, it's not yet a whole scripting language.
> > 
> > Before thinking about it as an ABI, we should develop it, extend
> > it, use these extensions, spot the weaknesses in the syntax, fix them,
> > etc...
> 
> Then this is a NACK for the perf ioctl for setting a filter. Fine with
> me.

Ftrace side (debugfs use):

I think the native filter glob is good for ftrace use through debugfs.
As I said, IMO it's so much a primary requirement for events filtering
that it should be a default.
But if others have mixed feelings about it, tell me and I will
reconsider. I've done this native glob in this patchset because the
general opinion (yours included) was in favour of that, instead of
a split into a filter and another filter_glob file.
That said, the future plans have evolved, and I'm fine if you have
changed your opinion and think about a better way to develop this.

Perf side:

But the use from perf would be for a larger scope. And I agree we may
want to break this glob default from it to get a flexible usability
and use a pure string match by default that we can override with
functions-like expressions.

So why not keeping the default native blob for ftrace and throw away
this default for perf? It's a matter of a flag in the filters.

You don't need to drop a NACK rock on the ground and laconically go out
like that to wake me up. I think I've already enough shown how much I'm
willing to help building a nice bridge between ftrace and perf.
I just don't want that this bridge turns out any ftrace uses through debugfs
into an overkill.
Instead I'd prefer to satisfy both, hence the above proposition.

Thanks,
Frederic.

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