Re: [PATCH v2] mm, page_isolation: remove drain_all_pages() in set_migratetype_isolate()

[Oscar Salvador <osalvador@suse.de>]

On Wed, Dec 19, 2018 at 04:46:56AM +0800, Wei Yang wrote:
> Below is a brief call flow for __offline_pages() and
> alloc_contig_range():
> 
>   __offline_pages()/alloc_contig_range()
>       start_isolate_page_range()
>           set_migratetype_isolate()
>               drain_all_pages()
>       drain_all_pages()
> 
> Current logic is: isolate and drain pcp list for each pageblock and
> drain pcp list again. This is not necessary and we could just drain pcp
> list once after isolate this whole range.
> 
> The reason is start_isolate_page_range() will set the migrate type of
> a range to MIGRATE_ISOLATE. After doing so, this range will never be
> allocated from Buddy, neither to a real user nor to pcp list.
> 
> Since drain_all_pages() is zone based, by reduce times of
> drain_all_pages() also reduce some contention on this particular zone.
> 
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>

It is a bit late and I hope I did not miss anything, but looks good to me.

Reviewed-by: Oscar Salvador <osalvador@suse.de>

Thanks!
-- 
Oscar Salvador
SUSE L3