linux-kernel - Re: [RFC] gcc feature request: Moving blocks into sections

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Message-ID: <51FFF430.1060701@linux.intel.com>
Date:	Mon, 05 Aug 2013 11:51:28 -0700
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, gcc <gcc@....gnu.org>,
	Ingo Molnar <mingo@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Daney <ddaney.cavm@...il.com>,
	Behan Webster <behanw@...verseincode.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [RFC] gcc feature request: Moving blocks into sections

On 08/05/2013 11:49 AM, Steven Rostedt wrote:
> On Mon, 2013-08-05 at 11:29 -0700, H. Peter Anvin wrote:
> 
>> Traps nest, that's why there is a stack.  (OK, so you don't want to take
>> the same trap inside the trap handler, but that code should be very
>> limited.)  The trap instruction just becomes very short, but rather
>> slow, call-return.
>>
>> However, when you consider the cost you have to consider that the
>> tracepoint is doing other work, so it may very well amortize out.
> 
> Also, how would you pass the parameters? Every tracepoint has its own
> parameters to pass to it. How would a trap know what where to get "prev"
> and "next"?
> 

How do you do that now?

You have to do an IP lookup to find out what you are doing.

(Note: I wonder how much the parameter generation costs the tracepoints.)

	-hpa


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