linux-kernel - Re: [RFC PATCH v2 -tip 0/4] x86: signal handler improvement

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Date:	Sat, 27 Sep 2008 19:11:35 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 -tip 0/4] x86: signal handler improvement


* H. Peter Anvin <hpa@...or.com> wrote:

> Hiroshi Shimamoto wrote:
>>>>
>>> This is a gcc failure, and should be reported to the gcc people.
>>
>> Does this gcc failure mean unnecessary storing into stack?
>
> Yes, it should be able to process this in a register, instead of 
> storing to the stack and then merging later.
>
> It's possible it's trying to do that to hide latency, but that's 
> clearly a lose in this case.
>
> I'd hate to obfuscate the code, and I'd *really* hate to obfuscate the 
> code to work around gcc brokenness, and then not even bothering to 
> tell the gcc folks.

assuming it's reported to the gcc folks too, do you have any objections 
against including this in tip/x86/signal? The 1% improvement in lmbench 
is quite nice.

	Ingo
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