linux-kernel - Re: [PATCH] percpu: add optimized generic percpu accessors

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Message-ID: <496FDE53.7010104@zytor.com>
Date:	Thu, 15 Jan 2009 17:09:39 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Herbert Xu <herbert@...dor.apana.org.au>,
	akpm@...ux-foundation.org, tj@...nel.org, brgerst@...il.com,
	ebiederm@...ssion.com, cl@...ux-foundation.org,
	rusty@...tcorp.com.au, travis@....com,
	linux-kernel@...r.kernel.org, steiner@....com, hugh@...itas.com
Subject: Re: [PATCH] percpu: add optimized generic percpu accessors

Ingo Molnar wrote:
>>
>> So if you could design the API such that we have a variant of add/inc 
>> that automatically disables/enables preemption then we can optimise that 
>> away on x86.
> 
> Yeah. percpu_add(var, 1) does exactly that on x86.
> 

And even on architectures which can only do percpu inc/dec we can make 
the right thing happen for a constant here, so we really don't need a 
new interface.  This is a good thing.

	-hpa
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