Date: Fri, 17 Apr 2009 18:23:26 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
       Steven Rostedt <rostedt@goodmis.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Subject: Re: [PATCH 1/4] tracing: move __DO_TRACE out of line
Message-ID: <20090417162326.GG8253@elte.hu>
References: <1239950139-1119-1-git-send-email-jeremy@goop.org> <1239950139-1119-2-git-send-email-jeremy@goop.org> <20090417154640.GB8253@elte.hu> <20090417161005.GA16361@Krystal>
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* Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:

> > > +#define DEFINE_DO_TRACE(name, proto, args)				\
> > > +	void __do_trace_##name(struct tracepoint *tp, TP_PROTO(proto))	\
> > > +	{								\
> > 
> > that needs to be marked notrace, otherwise the function tracer 
> > becomes noisy. (or even lockupy.)
> 
> I guess I'll have to put it more clearly : I am all for minimizing 
> tracepoint header dependency, but I'll be nacking this kind of 
> out-of-lining patch. Taking a function call, and moving it 
> out-of-line (thus duplicating the function call for nothing) seems 
> *really* pointless and will hurt tracer performance.

No need to nak - just say you dont like it and it gets fixed :)

I meant to suggest to Jeremy to measure the effect of this 
out-of-lining, in terms of instruction count in the hotpath.

> If thread_info.h is now so big that it needs a cleanup, I guess 
> we'll just have to do it.

Music to my ears ...

	Ingo
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