Messages in this thread | | | Date | Fri, 07 Feb 2014 10:20:57 +0100 | From | Vlastimil Babka <> | Subject | Re: [PATCH 1/5] mm/compaction: disallow high-order page for migration target |
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On 02/07/2014 06:08 AM, Joonsoo Kim wrote: > Purpose of compaction is to get a high order page. Currently, if we find > high-order page while searching migration target page, we break it to > order-0 pages and use them as migration target. It is contrary to purpose > of compaction, so disallow high-order page to be used for > migration target.
I guess this actually didn't trigger often because with large free blocks available, compaction shouldn't even be running (unless started manually). But the change makes sense.
> Additionally, clean-up logic in suitable_migration_target() to simply.
simply -> simplify the code.
> There is no functional changes from this clean-up. > > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
> diff --git a/mm/compaction.c b/mm/compaction.c > index 3a91a2e..bbe1260 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -217,21 +217,12 @@ static inline bool compact_trylock_irqsave(spinlock_t *lock, > /* Returns true if the page is within a block suitable for migration to */ > static bool suitable_migration_target(struct page *page) > { > - int migratetype = get_pageblock_migratetype(page); > - > - /* Don't interfere with memory hot-remove or the min_free_kbytes blocks */ > - if (migratetype == MIGRATE_RESERVE) > - return false; > - > - if (is_migrate_isolate(migratetype)) > - return false; > - > - /* If the page is a large free page, then allow migration */ > + /* If the page is a large free page, then disallow migration */ > if (PageBuddy(page) && page_order(page) >= pageblock_order) > - return true; > + return false; > > /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */ > - if (migrate_async_suitable(migratetype)) > + if (migrate_async_suitable(get_pageblock_migratetype(page))) > return true; > > /* Otherwise skip the block */ >
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