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

[Gioh Kim]

2014-07-08 ìì 12:57, Vlastimil Babka ì ê:
> 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@xxxxxxx>
> > ---
> >   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 */
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