linux-kernel - Re: [patch 7/9] LTTng instrumentation

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Message-Id: <200903251143.12472.rusty@rustcorp.com.au>
Date:	Wed, 25 Mar 2009 11:43:11 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	ltt-dev@...ts.casi.polymtl.ca,
	Frederic Weisbecker <fweisbec@...il.com>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Hideo AOKI <haoki@...hat.com>,
	Takashi Nishiie <t-nishiie@...css.fujitsu.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Eduard - Gabriel Munteanu" <eduard.munteanu@...ux360.ro>
Subject: Re: [patch 7/9] LTTng instrumentation - kernel

On Wednesday 25 March 2009 05:03:13 Ingo Molnar wrote:
> 
> (Rusty Cc:-ed - for the module.c tracepoints below)

Thanks, tho they look fine and non-intrusive to me.

> I believe that to have a complete picture of module usage, module 
> refcount get/put events should be included as well, beyond the basic 
> load/free events.
> 
> These both have performance impact (a module get/put in a fastpath 
> hurts scalability), and are informative in terms of establishing the 
> module dependency graph.

A module_get()/put() should not hurt scalability at all!  I went to great and
horrible lengths to ensure that was the case since the rewrite in 2.4.

But a module dependency graph et. al. would be kind of cool.

Thanks,
Rusty.
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