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Date: Tue, 27 Dec 2005 16:41:28 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Eric Dumazet <dada1@cosmosbay.com>
Cc: lkml <linux-kernel@vger.kernel.org>, Linus Torvalds <torvalds@osdl.org>,
       Andrew Morton <akpm@osdl.org>, Arjan van de Ven <arjan@infradead.org>,
       Nicolas Pitre <nico@cam.org>, Jes Sorensen <jes@trained-monkey.org>,
       Zwane Mwaikambo <zwane@arm.linux.org.uk>,
       Oleg Nesterov <oleg@tv-sign.ru>, David Howells <dhowells@redhat.com>,
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       Christoph Hellwig <hch@infradead.org>, Andi Kleen <ak@suse.de>,
       Russell King <rmk+lkml@arm.linux.org.uk>
Subject: Re: [patch 04/11] mutex subsystem, add include/asm-x86_64/mutex.h
Message-ID: <20051227154128.GA15961@elte.hu>
References: <20051227141548.GE6660@elte.hu> <43B158A6.7080508@cosmosbay.com>
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* Eric Dumazet <dada1@cosmosbay.com> wrote:

> >+		:"=D" (dummy)						\
> >+		: "D" (v)						\
> >+		: "rax", "rsi", "rdx", "rcx",				\
> >+		  "r8", "r9", "r10", "r11", "memory");			\
> >+} while (0)
> 
> Hi Ingo
> 
> I do think this assembly is not very fair. It has an *insane* register 
> pressure for the compiler : The fast path is thus not so fast.

if you look at the compiler output you'll notice that it's not a problem 
actually: this fastpath is only inlined into the generic code, where it 
has no clobbering side-effects.

you are right in that if this were to be inlined left and right, this 
would be quite bad.

	Ingo