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From: Jason Baron <jbaron@redhat.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu,
	mathieu.desnoyers@polymtl.ca, tglx@linutronix.de,
	rostedt@goodmis.org, andi@firstfloor.org, roland@redhat.com,
	rth@redhat.com, mhiramat@redhat.com, fweisbec@gmail.com,
	avi@redhat.com, davem@davemloft.net, vgoyal@redhat.com,
	sam@ravnborg.org, tony@bakeyournoodle.com
Subject: Re: [PATCH 08/10] jump label v11: x86 support
Date: Tue, 21 Sep 2010 11:25:25 -0400	[thread overview]
Message-ID: <20100921152525.GC2873@redhat.com> (raw)
In-Reply-To: <4C981BC4.90405@zytor.com>

On Mon, Sep 20, 2010 at 07:43:16PM -0700, H. Peter Anvin wrote:
> On 09/17/2010 08:09 AM, Jason Baron wrote:
> > add x86 support for jump label. I'm keeping this patch separate so its clear to
> > arch maintainers what was required for x86 support this new feature. hopefully,
> > it wouldn't be too painful for other arches.
> 
> > +	select HAVE_ARCH_JUMP_LABEL if !CC_OPTIMIZE_FOR_SIZE
> 
> Why?
> 
> 	-hpa
> 

Hi,

>From the documentation patch:

"
The optimization depends on !CC_OPTIMIZE_FOR_SIZE. When CC_OPTIMIZE_FOR_SIZE is
set, gcc does not always out of line the not taken label path in the same way
that the "if unlikely()" paths are made out of line. Thus, with
CC_OPTIMIZE_FOR_SIZE set, this optimization is not always optimal. This may be
solved in subsequent gcc versions, that allow us to move labels out of line,
while still optimizing for size.
"

This was also discuessed a bit on lkml previously:

http://marc.info/?l=linux-kernel&m=127618233108964&w=2


thanks,

-Jason




  reply	other threads:[~2010-09-21 15:26 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-09-17 15:08 [PATCH 00/10] jump label v11 Jason Baron
2010-09-17 15:08 ` [PATCH 01/10] jump label v11: make dynamic no-op selection available outside of ftrace Jason Baron
2010-09-17 15:28   ` Steven Rostedt
2010-09-24  8:58   ` [tip:perf/core] jump label: Make " tip-bot for Jason Baron
2010-09-17 15:08 ` [PATCH 02/10] jump label v11: make text_poke_early() globally visisble Jason Baron
2010-09-24  8:58   ` [tip:perf/core] jump label: Make text_poke_early() globally visible tip-bot for Jason Baron
2010-09-17 15:09 ` [PATCH 03/10] jump label v11: base patch Jason Baron
2010-09-17 18:21   ` David Miller
2010-09-21  2:37   ` Steven Rostedt
2010-09-21 13:12   ` Andi Kleen
2010-09-21 14:35     ` Jason Baron
2010-09-21 14:41       ` Andi Kleen
2010-09-21 15:04         ` Jason Baron
2010-09-21 15:09         ` Ingo Molnar
2010-09-21 15:14         ` Steven Rostedt
2010-09-21 17:35           ` H. Peter Anvin
2010-09-21 17:42             ` Andi Kleen
2010-09-21 17:36           ` Andi Kleen
2010-09-21 18:05             ` Steven Rostedt
2010-09-21 18:24               ` Mathieu Desnoyers
2010-09-21 19:48                 ` Andi Kleen
2010-09-21 18:48               ` Andi Kleen
2010-09-21 17:39           ` Andi Kleen
2010-09-21 18:29   ` Konrad Rzeszutek Wilk
2010-09-21 18:55     ` Konrad Rzeszutek Wilk
2010-09-21 18:58       ` H. Peter Anvin
2010-09-24  8:59   ` [tip:perf/core] jump label: Base patch for jump label tip-bot for Jason Baron
2010-09-17 15:09 ` [PATCH 04/10] jump label v11: initialize workqueue tracepoints *before* they are registered Jason Baron
2010-09-24  8:59   ` [tip:perf/core] jump label: Initialize " tip-bot for Jason Baron
2010-09-17 15:09 ` [PATCH 05/10] jump label v11: jump_label_text_reserved() to reserve our jump points Jason Baron
2010-09-24  9:00   ` [tip:perf/core] jump label: Add jump_label_text_reserved() to reserve " tip-bot for Jason Baron
2010-09-17 15:09 ` [PATCH 06/10] jump label v11: tracepoint support Jason Baron
2010-09-24  9:00   ` [tip:perf/core] jump label: Tracepoint support for jump labels tip-bot for Jason Baron
2010-09-17 15:09 ` [PATCH 07/10] jump label v11: convert dynamic debug to use " Jason Baron
2010-09-24  9:00   ` [tip:perf/core] jump label: Convert " tip-bot for Jason Baron
2010-09-17 15:09 ` [PATCH 08/10] jump label v11: x86 support Jason Baron
2010-09-21  2:32   ` Steven Rostedt
2010-09-21  2:43   ` H. Peter Anvin
2010-09-21 15:25     ` Jason Baron [this message]
2010-09-21 15:29       ` Ingo Molnar
2010-09-21 15:35         ` Steven Rostedt
2010-09-21 16:33           ` Jason Baron
2010-09-21 18:30   ` Konrad Rzeszutek Wilk
2010-09-24  9:01   ` [tip:perf/core] jump label: " tip-bot for Jason Baron
2010-09-24 16:19     ` H. Peter Anvin
2010-09-24 16:34       ` Jason Baron
2010-09-24 17:30         ` H. Peter Anvin
2010-09-24 18:08           ` Steven Rostedt
2010-10-18 11:17     ` Peter Zijlstra
2010-10-18 12:48       ` Mathieu Desnoyers
2010-09-17 15:09 ` [PATCH 09/10] jump label 11: add sparc64 support Jason Baron
2010-09-20 22:25   ` Steven Rostedt
2010-09-20 22:30     ` David Miller
2010-09-20 22:38       ` Steven Rostedt
2010-09-21 15:37   ` Steven Rostedt
2010-09-21 16:27     ` David Miller
2010-09-23  3:09       ` Steven Rostedt
2010-09-24  9:01   ` [tip:perf/core] jump label: Add " tip-bot for David S. Miller
2010-09-17 15:09 ` [PATCH 10/10] jump label v11: add docs Jason Baron
2010-09-17 16:05   ` Mathieu Desnoyers
2010-09-20 22:28     ` Steven Rostedt
2010-09-21 16:20       ` Jason Baron
2010-09-21  8:20   ` matt mooney
2010-09-21 18:39   ` Konrad Rzeszutek Wilk

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