Re: [Linaro-mm-sig] [PATCH 05/11] mm: mmzone: MIGRATE_CMA migration type added

On Thu, Dec 29, 2011 at 01:39:06PM +0100, Marek Szyprowski wrote:

From: Michal Nazarewicz mina86@mina86.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 (to some degree) 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 for allocating big chunks (eg. 10MiB) of physically contiguous memory. Once driver requests contiguous memory, pages from MIGRATE_CMA pageblocks may be migrated away to create a contiguous block.

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 mina86@mina86.com [m.szyprowski: removed CONFIG_CMA_MIGRATE_TYPE] Signed-off-by: Marek Szyprowski m.szyprowski@samsung.com Signed-off-by: Kyungmin Park kyungmin.park@samsung.com

---

include/linux/mmzone.h | 41 ++++++++++++++++++++---- include/linux/page-isolation.h | 3 ++ mm/Kconfig | 2 +- mm/compaction.c | 11 +++++-- mm/page_alloc.c | 68 ++++++++++++++++++++++++++++++--------- mm/vmstat.c | 1 + 6 files changed, 99 insertions(+), 27 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 188cb2f..e38b85d 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -35,13 +35,35 @@ */ #define PAGE_ALLOC_COSTLY_ORDER 3 -#define MIGRATE_UNMOVABLE 0 -#define MIGRATE_RECLAIMABLE 1 -#define MIGRATE_MOVABLE 2 -#define MIGRATE_PCPTYPES 3 /* the number of types on the pcp lists */ -#define MIGRATE_RESERVE 3 -#define MIGRATE_ISOLATE 4 /* can't allocate from here */ -#define MIGRATE_TYPES 5 +enum {

• MIGRATE_UNMOVABLE,
• MIGRATE_RECLAIMABLE,
• MIGRATE_MOVABLE,
• MIGRATE_PCPTYPES, /* the number of types on the pcp lists */
• MIGRATE_RESERVE = MIGRATE_PCPTYPES,
• /*

• * 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,
• MIGRATE_ISOLATE, /* can't allocate from here */
• MIGRATE_TYPES

+};

MIGRATE_CMA is being added whether or not CONFIG_CMA is set. This increases the size of the pageblock bitmap and where that is just 1 bit per pageblock in the system, it may be noticable on large machines.

+#ifdef CONFIG_CMA +# define is_migrate_cma(migratetype) unlikely((migratetype) == MIGRATE_CMA) +#else +# define is_migrate_cma(migratetype) false +#endif

Use static inlines.

#define for_each_migratetype_order(order, type) \ for (order = 0; order < MAX_ORDER; order++) \ @@ -54,6 +76,11 @@ static inline int get_pageblock_migratetype(struct page *page) return get_pageblock_flags_group(page, PB_migrate, PB_migrate_end); } +static inline bool is_pageblock_cma(struct page *page) +{

• return is_migrate_cma(get_pageblock_migratetype(page));

+}

This allows additional calls to get_pageblock_migratetype() even if CONFIG_CMA is not set.

struct free_area { struct list_head free_list[MIGRATE_TYPES]; unsigned long nr_free; diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h index d305080..af650db 100644 --- a/include/linux/page-isolation.h +++ b/include/linux/page-isolation.h @@ -37,4 +37,7 @@ extern void unset_migratetype_isolate(struct page *page); int alloc_contig_range(unsigned long start, unsigned long end); void free_contig_range(unsigned long pfn, unsigned nr_pages); +/* CMA stuff */ +extern void init_cma_reserved_pageblock(struct page *page);

#endif diff --git a/mm/Kconfig b/mm/Kconfig index 011b110..e080cac 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -192,7 +192,7 @@ config COMPACTION config MIGRATION bool "Page migration" def_bool y

• depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION

• depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA help Allows the migration of the physical location of pages of processes while the virtual addresses are not changed. This is useful in

diff --git a/mm/compaction.c b/mm/compaction.c index 8733441..46783b4 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -21,6 +21,11 @@ #define CREATE_TRACE_POINTS #include <trace/events/compaction.h> +static inline bool is_migrate_cma_or_movable(int migratetype) +{

• return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE;

+}

That is not a name that helps any. migrate_async_suitable() would be marginally better.

/**

• isolate_freepages_range() - isolate free pages, must hold zone->lock.
• @zone: Zone pages are in.

@@ -213,7 +218,7 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, */ pageblock_nr = low_pfn >> pageblock_order; if (!cc->sync && last_pageblock_nr != pageblock_nr &&

• 		get_pageblock_migratetype(page) != MIGRATE_MOVABLE) {
  

•     is_migrate_cma_or_movable(get_pageblock_migratetype(page))) {
  low_pfn += pageblock_nr_pages;
  low_pfn = ALIGN(low_pfn, pageblock_nr_pages) - 1;
  last_pageblock_nr = pageblock_nr;
  

I know I suggested migrate_async_suitable() here but the check may not even happen if CMA uses sync migration.

@@ -295,8 +300,8 @@ static bool suitable_migration_target(struct page *page) if (PageBuddy(page) && page_order(page) >= pageblock_order) return true;

• /* If the block is MIGRATE_MOVABLE, allow migration */
• if (migratetype == MIGRATE_MOVABLE)

• /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
• if (is_migrate_cma_or_movable(migratetype)) return true;

/* Otherwise skip the block */ diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 47b0a85..06a7861 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -722,6 +722,26 @@ void __meminit __free_pages_bootmem(struct page *page, unsigned int order) } } +#ifdef CONFIG_CMA +/*

• • Free whole pageblock and set it's migration type to MIGRATE_CMA.
• */

+void __init init_cma_reserved_pageblock(struct page *page) +{

• unsigned i = pageblock_nr_pages;
• struct page *p = page;
• do {

• __ClearPageReserved(p);
  

• set_page_count(p, 0);
  

• } while (++p, --i);
• set_page_refcounted(page);
• set_pageblock_migratetype(page, MIGRATE_CMA);
• __free_pages(page, pageblock_order);
• totalram_pages += pageblock_nr_pages;

+} +#endif /*

• The order of subdivision here is critical for the IO subsystem.

@@ -830,11 +850,10 @@ 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_PCPTYPES][4] = { [MIGRATE_UNMOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE, MIGRATE_RESERVE }, [MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE, MIGRATE_MOVABLE, MIGRATE_RESERVE },

• [MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_RESERVE },
• [MIGRATE_RESERVE] = { MIGRATE_RESERVE, MIGRATE_RESERVE, MIGRATE_RESERVE }, /* Never used */

• [MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_CMA , MIGRATE_RESERVE },

Why did you delete [MIGRATE_RESERVE] here? It changes the array from being expressed in terms of MIGRATE_TYPES to being a hard-coded value. I do not see the advantage and it's not clear how it is related to the patch.

}; /* @@ -929,12 +948,12 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype) /* Find the largest possible block of pages in the other list */ for (current_order = MAX_ORDER-1; current_order >= order; --current_order) {

• for (i = 0; i < MIGRATE_TYPES - 1; i++) {
  

• for (i = 0; i < ARRAY_SIZE(fallbacks[0]); i++) {
  migratetype = fallbacks[start_migratetype][i];
  

/* MIGRATE_RESERVE handled later if necessary */ if (migratetype == MIGRATE_RESERVE)

• 		continue;
  

• 		break;
  

area = &(zone->free_area[current_order]); if (list_empty(&area->free_list[migratetype])) @@ -949,11 +968,18 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype) * pages to the preferred allocation list. If falling * back for a reclaimable kernel allocation, be more * aggressive about taking ownership of free pages

• 	 *
  

• 	 * On the other hand, never change migration
  

• 	 * type of MIGRATE_CMA pageblocks nor move CMA
  

• 	 * pages on different free lists. We don't
  

• 	 * want unmovable pages to be allocated from
  

• 	 * MIGRATE_CMA areas.
   */
  

• 	if (unlikely(current_order >= (pageblock_order >> 1)) ||
  

• 			start_migratetype == MIGRATE_RECLAIMABLE ||
  

• 			page_group_by_mobility_disabled) {
  

• 		unsigned long pages;
  

• 	if (!is_pageblock_cma(page) &&
  

• 	    (unlikely(current_order >= pageblock_order / 2) ||
  

• 	     start_migratetype == MIGRATE_RECLAIMABLE ||
  

• 	     page_group_by_mobility_disabled)) {
  

• 		int pages;
  	pages = move_freepages_block(zone, page,
  					start_migratetype);
  

@@ -971,11 +997,14 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype) rmv_page_order(page); /* Take ownership for orders >= pageblock_order */

• 	if (current_order >= pageblock_order)
  

• 	if (current_order >= pageblock_order &&
  

• 	    !is_pageblock_cma(page))
  	change_pageblock_range(page, current_order,
  				start_migratetype);
  

• 	expand(zone, page, order, current_order, area, migratetype);
  

• 	expand(zone, page, order, current_order, area,
  

• 	       is_migrate_cma(start_migratetype)
  

• 	     ? start_migratetype : migratetype);
  

trace_mm_page_alloc_extfrag(page, order, current_order, start_migratetype, migratetype); @@ -1047,7 +1076,10 @@ 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);
  

• if (is_pageblock_cma(page))
  

• 	set_page_private(page, MIGRATE_CMA);
  

• else
  

• 	set_page_private(page, migratetype);
  

  list = &page->lru; } __mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order));

@@ -1308,8 +1340,12 @@ int split_free_page(struct page *page) if (order >= pageblock_order - 1) { struct page *endpage = page + (1 << order) - 1;

• for (; page < endpage; page += pageblock_nr_pages)
  

• 	set_pageblock_migratetype(page, MIGRATE_MOVABLE);
  

• for (; page < endpage; page += pageblock_nr_pages) {
  

• 	int mt = get_pageblock_migratetype(page);
  

• 	if (mt != MIGRATE_ISOLATE && !is_migrate_cma(mt))
  

• 		set_pageblock_migratetype(page,
  

• 					  MIGRATE_MOVABLE);
  

• }
  

  }

return 1 << order; @@ -5599,8 +5635,8 @@ __count_immobile_pages(struct zone *zone, struct page *page, int count) */ if (zone_idx(zone) == ZONE_MOVABLE) return true;

• if (get_pageblock_migratetype(page) == MIGRATE_MOVABLE)

• if (get_pageblock_migratetype(page) == MIGRATE_MOVABLE ||

•    is_pageblock_cma(page))
  

  return true;

pfn = page_to_pfn(page); diff --git a/mm/vmstat.c b/mm/vmstat.c index 8fd603b..9fb1789 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -613,6 +613,7 @@ static char * const migratetype_names[MIGRATE_TYPES] = { "Reclaimable", "Movable", "Reserve",

• "Cma", "Isolate",

}; -- 1.7.1.569.g6f426