Re: [PATCH 08/10] mm/page_alloc: use get_onbuddy_migratetype() to get buddy list type

[Gioh Kim <gioh.kim@lge.com>]

2014-07-08 오전 12:57, Vlastimil Babka 쓴 글:
> On 07/04/2014 09:57 AM, Joonsoo Kim wrote:
>> When isolating free page, what we want to know is which list
>> the page is linked. If it is linked in isolate migratetype buddy list,
>> we can skip watermark check and freepage counting. And if it is linked
>> in CMA migratetype buddy list, we need to fixup freepage counting. For
>> this purpose, get_onbuddy_migratetype() is more fit and cheap than
>> get_pageblock_migratetype(). So use it.
>
> Hm but you made get_onbuddy_migratetype() work only with CONFIG_MEMORY_ISOLATION. And __isolate_free_page is (despite the name) not at all limited to CONFIG_MEMORY_ISOLATION.
>

Current __isolate_free_page is called by only split_free_page, and split_free_page by isolate_freepages_block.
split_free_page is called only for isolated pages now but It can be changed someday.
I think get_onbuddy_migratetype should work with any situation.

And I think the name of get_onbuddy_migratetype is confused.
Because of _onbuddy_, it might look like that the pages are buddy pages.
I think the original name _freepage_ is proper one.


>> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>> ---
>>   mm/page_alloc.c |    2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index e1c4c3e..d9fb8bb 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -1597,7 +1597,7 @@ static int __isolate_free_page(struct page *page, unsigned int order)
>>       BUG_ON(!PageBuddy(page));
>>
>>       zone = page_zone(page);
>> -    mt = get_pageblock_migratetype(page);
>> +    mt = get_onbuddy_migratetype(page);
>>
>>       if (!is_migrate_isolate(mt)) {
>>           /* Obey watermarks as if the page was being allocated */
>>
>
>