linux-kernel - Re: [PATCH] account_system_vtime() should be a macro, not a function

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Date:	Thu, 19 Oct 2006 15:46:02 +0200
From:	Andi Kleen <ak@...e.de>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	Andrew Morton <akpm@...l.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] account_system_vtime() should be a macro, not a function

On Thursday 19 October 2006 15:43, Eric Dumazet wrote:
> [PATCH] account_system_vtime() should be a macro, not a function
> 
> Because the way 'current' is implemented on some archs, it's better to use a 
> null macro for account_system_vtime(current) 
> 
> I discovered that gcc was (correctly) issuing one useless instruction (to 
> load %rax with current from pda) on x86_64 on irq_enter() and __irq_exit()
> 
> This saves few bytes in kernel size, on archs where current is 'asm volatile'

I dropped the asm volatile on x86-64 some time ago. Perhaps it should
be dropped on the other architectures too.  Then such hacks wouldn't
be needed anywhere.

-Andi
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