linux-kernel - Re: [PATCH 2/4] seq_file: Add seq_cpumask_list(), seq_nodemask

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Message-ID: <48F7C69E.3060509@sgi.com>
Date:	Thu, 16 Oct 2008 15:56:30 -0700
From:	Mike Travis <travis@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Lai Jiangshan <laijs@...fujitsu.com>, adobriyan@...il.com,
	menage@...gle.com, pj@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] seq_file: Add seq_cpumask_list(), seq_nodemask_list()

Andrew Morton wrote:
> On Sun, 12 Oct 2008 17:29:25 +0800
> Lai Jiangshan <laijs@...fujitsu.com> wrote:
> 
>> +static inline int seq_cpumask_list(struct seq_file *m, cpumask_t *mask)
>> +{
>> +	return seq_bitmap_list(m, mask->bits, NR_CPUS);
>> +}
> 
> Is it possible to avoid using NR_CPUS?  In some situations it'd be much
> more efficient to use the runtime-determined max possible cpu index.
> 
> But I don't immediately recall how to get at that number. 
> num_possible_cpus() assumes that there are no holes in the CPU
> identifier list.
> 

nr_cpu_ids represents the max index +1 of the possible cpus.  (Usually the
same as num_possible_cpus() except a.) it doesn't need to do the cpus_weight()
op, and b.) *if* (a big if) the cpu indices are sparse, then they wouldn't
be the same values.)

Thanks,
Mike
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