linux-kernel - Re: [RFC][PATCH] tracepoints: Move the work out of line from hotpath sections

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Message-ID: <1344562886.6935.93.camel@gandalf.stny.rr.com>
Date:	Thu, 09 Aug 2012 21:41:26 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	David Daney <ddaney.cavm@...il.com>
Cc:	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Avi Kivity <avi@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC][PATCH] tracepoints: Move the work out of line from
 hotpath sections

On Thu, 2012-08-09 at 16:54 -0700, David Daney wrote:
> On 08/09/2012 04:16 PM, H. Peter Anvin wrote:
> > On 08/09/2012 03:25 PM, Steven Rostedt wrote:
> >>>
> >>> It might be better to improve gcc to move really cold branches out of
> >>> line (really, really far away), and use the compiler to do this, rather
> >>> than to use an extra indirection that adds bloat and complexity to the
> >>> kernel.
> 
> Oh, you mean like: -freorder-blocks-and-partition

Actually, what would be really nice is to place a block in a section of
your choice. Something like:


	if (unlikely(x)) __attribute__((section(".unlikely"))) {
		/* code here will be in the ".unlikely" section */
	}

-- Steve


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