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Message-ID: <20090428205154.GE13893@redhat.com>
Date: Tue, 28 Apr 2009 16:51:54 -0400
From: "Frank Ch. Eigler" <fche@...hat.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: zhaolei@...fujitsu.com, mingo@...e.hu,
kosaki.motohiro@...fujitsu.com, fweisbec@...il.com,
rostedt@...dmis.org, tzanussi@...il.com,
linux-kernel@...r.kernel.org, oleg@...hat.com
Subject: Re: [PATCH 0/4] workqueue_tracepoint: Add worklet tracepoints for worklet lifecycle tracing
Hi, Andrew -
On Tue, Apr 28, 2009 at 11:48:27AM -0700, Andrew Morton wrote:
> [...]
> > To be fair, if you ask for someone to specify and quantify the
> > "benefits" side of this, shouldn't someone specify and quantify the
> > "cost" side of this too?
> [...]
> > That way we would have something to compare.
>
> Well, there are two aspects to this. There's the immediate up-front
> cost - a little added complexity, more code, etc.
Yes, a little.
> But there's also the where-the-hell-is-this-all-going question. Are we
> going to end up with hundreds or thousands of tracepoints sprinkled all
> over core kernel? If so, what use are they? What userspace tools will
> be used to pull them into something useful? Who will be developing
> those tools and are they involved in the development of the
> tracepoints?
(Well, that's back to the "benefits" side, isn't it?)
> Will this proliferation of static tracepoints actively kill off the
> development and maturation of dynamic tracepoints? If so, is that
> good?
I hope not, but I believe the consensus has been that both dynamic and
static instrumentation are necessary & useful.
> From where I sit it looks like a mad scramble to sprinkle fairly
> random tracepoints all over the place under the assumption that
> this-may-be-useful-to-someone-one-day. But of course, that means
> that they many never be useful to anyone ever. [...]
You may not be giving enough credit to the subsystem developers. If
they opine that those tracepoints may accomplish (or have already
accomplished) something forseeably useful, at a reasonably "little"
cost, should it not require a large burden of proof to overcome their
judgement?
- FChE
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