Re: [PATCH 2/4] seq_file: Add seq_cpumask_list(), seq_nodemask_list()

[Mike Travis <travis@sgi.com>]

Andrew Morton wrote:
> On Sun, 12 Oct 2008 17:29:25 +0800
> Lai Jiangshan <laijs@cn.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