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Date: Thu, 5 Jan 2006 06:00:50 -0800
From: Andrew Morton <akpm@osdl.org>
To: Eric Dumazet <dada1@cosmosbay.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] reduce sizeof(percpu_data) and removes dependance
 against NR_CPUS
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Eric Dumazet <dada1@cosmosbay.com> wrote:
>
> Current sizeof(percpu_data) is NR_CPUS*sizeof(void *)
> 
>  This trivial patch makes percpu_data real size depends on 
>  highest_possible_processor_id() instead of NR_CPUS
> 
>  percpu_data allocations are not performance critical, we can spend few CPU 
>  cycles and save some ram.

hm, highest_possible_processor_id() isn't very efficient.  And it's quite
dopey that it's a macro.  We should turn it into a real function which
caches its return result and goes BUG if it's called before
cpu_possible_map is initialised.