linux-kernel - Re: [patch 0/2] Immediate Values

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Message-ID: <481E2516.7070600@zytor.com>
Date:	Sun, 04 May 2008 14:05:26 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
CC:	Ingo Molnar <mingo@...e.hu>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, "Frank Ch. Eigler" <fche@...hat.com>
Subject: Re: [patch 0/2] Immediate Values - jump patching update

Mathieu Desnoyers wrote:
> 
> Following your own suggestion, why don't we fix gcc and make it
> interleave unlikely blocks less heavily with hot blocks ?
> 

Doing this with compiler support is definitely The Right Thing, so I 
think this is the best way.

>> Furthermore, modern CPUs often speculatively fetch *both* 
>> branches of a conditional.
>>
>> This is actually the biggest motivation for patching static branches.
> 
> Agreed. I'd like to find some info about which microarchitectures you
> have in mind. Intel Core 2 ?

Not sure about Core 2, although Core 2 definitely can track down the 
wrong branch on a mispredict.

> Let's fix gcc ! ;)

Sounds great :)

	-hpa

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