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SubjectRe: [PATCH v3 2/2] mm/sparse: start using sparse_init_nid(), and remove old code
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On 07/02/2018 03:47 PM, Dave Hansen wrote:
> On 07/01/2018 07:04 PM, Pavel Tatashin wrote:
>> + for_each_present_section_nr(pnum_begin + 1, pnum_end) {
>> + int nid = sparse_early_nid(__nr_to_section(pnum_end));
>>
>> + if (nid == nid_begin) {
>> + map_count++;
>> continue;
>> }
>
>> + sparse_init_nid(nid_begin, pnum_begin, pnum_end, map_count);
>> + nid_begin = nid;
>> + pnum_begin = pnum_end;
>> + map_count = 1;
>> }
>
> Ugh, this is really hard to read. Especially because the pnum "counter"
> is called "pnum_end".

I called it pnum_end, because that is what is passed to sparse_init_nid(), but I see your point, and I can rename pnum_end to simply pnum if that will make things look better.

>
> So, this is basically a loop that collects all of the adjacent sections
> in a given single nid and then calls sparse_init_nid(). pnum_end in
> this case is non-inclusive, so the sparse_init_nid() call is actually
> for the *previous* nid that pnum_end is pointing _past_.
>
> This *really* needs commenting.

There is a comment before sparse_init_nid() about inclusiveness:

434 /*
435 * Initialize sparse on a specific node. The node spans [pnum_begin, pnum_end)
436 * And number of present sections in this node is map_count.
437 */
438 static void __init sparse_init_nid(int nid, unsigned long pnum_begin,
439 unsigned long pnum_end,
440 unsigned long map_count)


Thank you,
Pavel

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