lkml.org 
[lkml]   [2014]   [Dec]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/3] mm: page_isolation: remove unnecessary freepage_migratetype check for unused page
On 12/09/2014 08:51 AM, Weijie Yang wrote:
> when we test the pages in a range is free or not, there is a little
> chance we encounter some page which is not in buddy but page_count is 0.
> That means that page could be in the page-freeing path but not in the
> buddy freelist, such as in pcplist

This shouldn't happen anymore IMHO. The pageblock is marked as
MIGRATE_ISOLATE and then a lru+pcplist drain is performed. Nothing
should be left on pcplist - anything newly freed goes directly to free
lists. Hm, maybe it could be on lru cache, but that holds a page
reference IIRC, so this test won't pass.

> or wait for the zone->lock which the
> tester is holding.

That could maybe happen, but is it worth testing? If yes, please add it
in a comment to the code.

> Back to the freepage_migratetype, we use it for a cached value for decide
> which free-list the page go when freeing page. If the pageblock is isolated
> the page will go to free-list[MIGRATE_ISOLATE] even if the cached type is
> not MIGRATE_ISOLATE, the commit ad53f92e(fix incorrect isolation behavior
> by rechecking migratetype) patch series have ensure this.
>
> So the freepage_migratetype check for page_count==0 page in
> __test_page_isolated_in_pageblock() is meaningless.
> This patch removes the unnecessary freepage_migratetype check.
>
> Signed-off-by: Weijie Yang <weijie.yang@samsung.com>
> ---
> mm/page_isolation.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index 6e5174d..f7c9183 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -223,8 +223,7 @@ __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
> page = pfn_to_page(pfn);
> if (PageBuddy(page))
> pfn += 1 << page_order(page);
> - else if (page_count(page) == 0 &&
> - get_freepage_migratetype(page) == MIGRATE_ISOLATE)
> + else if (page_count(page) == 0)
> pfn += 1;
> else if (skip_hwpoisoned_pages && PageHWPoison(page)) {
> /*
>



\
 
 \ /
  Last update: 2014-12-09 11:01    [W:0.048 / U:0.288 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site