On 01/30/2015 01:34 PM, Joonsoo Kim wrote:
> From: Joonsoo <iamjoonsoo.kim@xxxxxxx>
>
> This is preparation step to use page allocator's anti fragmentation logic
> in compaction. This patch just separates steal decision part from actual
> steal behaviour part so there is no functional change.
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> ---
> mm/page_alloc.c | 49 ++++++++++++++++++++++++++++++++-----------------
> 1 file changed, 32 insertions(+), 17 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 8d52ab1..ef74750 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1122,6 +1122,24 @@ static void change_pageblock_range(struct page *pageblock_page,
> }
> }
>
> +static bool can_steal_freepages(unsigned int order,
> + int start_mt, int fallback_mt)
> +{
> + if (is_migrate_cma(fallback_mt))
> + return false;
> +
> + if (order >= pageblock_order)
> + return true;
> +
> + if (order >= pageblock_order / 2 ||
> + start_mt == MIGRATE_RECLAIMABLE ||
> + start_mt == MIGRATE_UNMOVABLE ||
> + page_group_by_mobility_disabled)
> + return true;
> +
> + return false;
> +}
> +
> /*
> * When we are falling back to another migratetype during allocation, try to
> * steal extra free pages from the same pageblocks to satisfy further
> @@ -1138,9 +1156,10 @@ static void change_pageblock_range(struct page *pageblock_page,
> * as well.
> */
> static void try_to_steal_freepages(struct zone *zone, struct page *page,
> - int start_type, int fallback_type)
> + int start_type)
It's actually not 'try_to_' anymore, is it? But could be, see below.
> {
> int current_order = page_order(page);
> + int pages;
>
> /* Take ownership for orders >= pageblock_order */
> if (current_order >= pageblock_order) {
> @@ -1148,19 +1167,12 @@ static void try_to_steal_freepages(struct zone *zone, struct page *page,
> return;
> }
>
> - if (current_order >= pageblock_order / 2 ||
> - start_type == MIGRATE_RECLAIMABLE ||
> - start_type == MIGRATE_UNMOVABLE ||
> - page_group_by_mobility_disabled) {
> - int pages;
> + pages = move_freepages_block(zone, page, start_type);
>
> - pages = move_freepages_block(zone, page, start_type);
> -
> - /* Claim the whole block if over half of it is free */
> - if (pages >= (1 << (pageblock_order-1)) ||
> - page_group_by_mobility_disabled)
> - set_pageblock_migratetype(page, start_type);
> - }
> + /* Claim the whole block if over half of it is free */
> + if (pages >= (1 << (pageblock_order-1)) ||
> + page_group_by_mobility_disabled)
> + set_pageblock_migratetype(page, start_type);
> }
>
> /* Remove an element from the buddy allocator from the fallback list */
> @@ -1170,6 +1182,7 @@ __rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype)
> struct free_area *area;
> unsigned int current_order;
> struct page *page;
> + bool can_steal;
>
> /* Find the largest possible block of pages in the other list */
> for (current_order = MAX_ORDER-1;
> @@ -1192,10 +1205,11 @@ __rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype)
> struct page, lru);
> area->nr_free--;
>
> - if (!is_migrate_cma(migratetype)) {
> + can_steal = can_steal_freepages(current_order,
> + start_migratetype, migratetype);
> + if (can_steal) {
can_steal is only used once, why not do if (can_steal_freepages()) directly?
Or, call can_steal_freepages() from try_to_steal_freepages() and make
try_to_steal_freepages() return its result. Then here it simplifies to:
if (!try_to_steal_freepages(...) && is_migrate_cma(...))
buddy_type = migratetype;
> try_to_steal_freepages(zone, page,
> - start_migratetype,
> - migratetype);
> + start_migratetype);
> } else {
> /*
> * When borrowing from MIGRATE_CMA, we need to
> @@ -1203,7 +1217,8 @@ __rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype)
> * itself, and we do not try to steal extra
> * free pages.
> */
> - buddy_type = migratetype;
> + if (is_migrate_cma(migratetype))
> + buddy_type = migratetype;
> }
>
> /* Remove the page from the freelists */
>
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