On Tuesday 05 July 2011, Marek Szyprowski wrote:
From: Michal Nazarewicz m.nazarewicz@samsung.com
The MIGRATE_CMA migration type has two main characteristics: (i) only movable pages can be allocated from MIGRATE_CMA pageblocks and (ii) page allocator will never change migration type of MIGRATE_CMA pageblocks.
This guarantees that page in a MIGRATE_CMA page block can always be migrated somewhere else (unless there's no memory left in the system).
It is designed to be used with Contiguous Memory Allocator (CMA) for allocating big chunks (eg. 10MiB) of physically contiguous memory. Once driver requests contiguous memory, CMA will migrate pages from MIGRATE_CMA pageblocks.
To minimise number of migrations, MIGRATE_CMA migration type is the last type tried when page allocator falls back to other migration types then requested.
Signed-off-by: Michal Nazarewicz m.nazarewicz@samsung.com Signed-off-by: Kyungmin Park kyungmin.park@samsung.com [m.szyprowski: cleaned up Kconfig, renamed some functions] Signed-off-by: Marek Szyprowski m.szyprowski@samsung.com CC: Michal Nazarewicz mina86@mina86.com
Acked-by: Arnd Bergmann arnd@arndb.de, but I noticed a few things:
cma migrate fixup
This text doesn't belong here.
+enum {
- MIGRATE_UNMOVABLE,
- MIGRATE_RECLAIMABLE,
- MIGRATE_MOVABLE,
- MIGRATE_PCPTYPES, /* the number of types on the pcp lists */
- MIGRATE_RESERVE = MIGRATE_PCPTYPES,
+#ifdef CONFIG_CMA_MIGRATE_TYPE
- /*
* MIGRATE_CMA migration type is designed to mimic the way* ZONE_MOVABLE works. Only movable pages can be allocated* from MIGRATE_CMA pageblocks and page allocator never* implicitly change migration type of MIGRATE_CMA pageblock.** The way to use it is to change migratetype of a range of* pageblocks to MIGRATE_CMA which can be done by* __free_pageblock_cma() function. What is important though* is that a range of pageblocks must be aligned to* MAX_ORDER_NR_PAGES should biggest page be bigger then* a single pageblock.*/- MIGRATE_CMA,
+#endif
- MIGRATE_ISOLATE, /* can't allocate from here */
- MIGRATE_TYPES
+};
It's not clear to me why you need this #ifdef. Does it hurt if the migration type is defined but not used?
@@ -198,6 +198,12 @@ config MIGRATION pages as migration can relocate pages to satisfy a huge page allocation instead of reclaiming. +config CMA_MIGRATE_TYPE
- bool
- help
This enables the use the MIGRATE_CMA migrate type, which lets lets CMAwork on almost arbitrary memory range and not only inside ZONE_MOVABLE.config PHYS_ADDR_T_64BIT def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
This is currently only selected on ARM with your patch set.
diff --git a/mm/compaction.c b/mm/compaction.c index 6cc604b..9e5cc59 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -119,6 +119,16 @@ static bool suitable_migration_target(struct page *page) if (migratetype == MIGRATE_ISOLATE || migratetype == MIGRATE_RESERVE) return false;
- /* Keep MIGRATE_CMA alone as well. */
- /*
* XXX Revisit. We currently cannot let compaction touch CMA* pages since compaction insists on changing their migration* type to MIGRATE_MOVABLE (see split_free_page() called from* isolate_freepages_block() above).*/- if (is_migrate_cma(migratetype))
return false;- /* If the page is a large free page, then allow migration */ if (PageBuddy(page) && page_order(page) >= pageblock_order) return true;
Do you plan to fix address this before merging the patch set, or is it harmless enough to get in this way?
/*
- The order of subdivision here is critical for the IO subsystem.
@@ -827,11 +852,15 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
- This array describes the order lists are fallen back to when
- the free lists for the desirable migrate type are depleted
*/ -static int fallbacks[MIGRATE_TYPES][MIGRATE_TYPES-1] = { +static int fallbacks[MIGRATE_TYPES][4] = { [MIGRATE_UNMOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE, MIGRATE_RESERVE }, [MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE, MIGRATE_MOVABLE, MIGRATE_RESERVE }, +#ifdef CONFIG_CMA_MIGRATE_TYPE
- [MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_CMA , MIGRATE_RESERVE },
+#else [MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_RESERVE },
- [MIGRATE_RESERVE] = { MIGRATE_RESERVE, MIGRATE_RESERVE, MIGRATE_RESERVE }, /* Never used */
+#endif
- [MIGRATE_RESERVE] = { MIGRATE_RESERVE }, /* Never used */
}; /* @@ -1044,7 +1086,12 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order, list_add(&page->lru, list); else list_add_tail(&page->lru, list);
set_page_private(page, migratetype);+#ifdef CONFIG_CMA_MIGRATE_TYPE
if (is_pageblock_cma(page))set_page_private(page, MIGRATE_CMA);else+#endif
set_page_private(page, migratetype);
I guess if you can get rid of the first #ifdef I mentioned above, these two can be removed as well, without causing any run-time overhead.
Arnd