mm: cma: discard clean pages during contiguous allocation instead of migration
Drop clean cache pages instead of migration during alloc_contig_range() to
minimise allocation latency by reducing the amount of migration that is
necessary. It's useful for CMA because latency of migration is more
important than evicting the background process's working set. In
addition, as pages are reclaimed then fewer free pages for migration
targets are required so it avoids memory reclaiming to get free pages,
which is a contributory factor to increased latency.
I measured elapsed time of __alloc_contig_migrate_range() which migrates
10M in 40M movable zone in QEMU machine.
Before - 146ms, After - 7ms
[akpm@linux-foundation.org: fix nommu build]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Mel Gorman <mgorman@suse.de>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Cc: Rik van Riel <riel@redhat.com>
Tested-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index b2cce64..bfe1f47 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -71,6 +71,17 @@
#endif
};
+enum ttu_flags {
+ TTU_UNMAP = 0, /* unmap mode */
+ TTU_MIGRATION = 1, /* migration mode */
+ TTU_MUNLOCK = 2, /* munlock mode */
+ TTU_ACTION_MASK = 0xff,
+
+ TTU_IGNORE_MLOCK = (1 << 8), /* ignore mlock */
+ TTU_IGNORE_ACCESS = (1 << 9), /* don't age */
+ TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
+};
+
#ifdef CONFIG_MMU
static inline void get_anon_vma(struct anon_vma *anon_vma)
{
@@ -164,16 +175,6 @@
int page_referenced_one(struct page *, struct vm_area_struct *,
unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
-enum ttu_flags {
- TTU_UNMAP = 0, /* unmap mode */
- TTU_MIGRATION = 1, /* migration mode */
- TTU_MUNLOCK = 2, /* munlock mode */
- TTU_ACTION_MASK = 0xff,
-
- TTU_IGNORE_MLOCK = (1 << 8), /* ignore mlock */
- TTU_IGNORE_ACCESS = (1 << 9), /* don't age */
- TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
-};
#define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
int try_to_unmap(struct page *, enum ttu_flags flags);
diff --git a/mm/internal.h b/mm/internal.h
index bbd7b34..8312d4f 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -356,5 +356,6 @@
unsigned long, unsigned long);
extern void set_pageblock_order(void);
-
+unsigned long reclaim_clean_pages_from_list(struct zone *zone,
+ struct list_head *page_list);
#endif /* __MM_INTERNAL_H */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cfd565db..cefd14e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5700,6 +5700,8 @@
break;
}
+ reclaim_clean_pages_from_list(cc.zone, &cc.migratepages);
+
ret = migrate_pages(&cc.migratepages,
__alloc_contig_migrate_alloc,
0, false, MIGRATE_SYNC);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index d16bf5a..1ee4b69 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -674,8 +674,10 @@
static unsigned long shrink_page_list(struct list_head *page_list,
struct zone *zone,
struct scan_control *sc,
+ enum ttu_flags ttu_flags,
unsigned long *ret_nr_dirty,
- unsigned long *ret_nr_writeback)
+ unsigned long *ret_nr_writeback,
+ bool force_reclaim)
{
LIST_HEAD(ret_pages);
LIST_HEAD(free_pages);
@@ -689,10 +691,10 @@
mem_cgroup_uncharge_start();
while (!list_empty(page_list)) {
- enum page_references references;
struct address_space *mapping;
struct page *page;
int may_enter_fs;
+ enum page_references references = PAGEREF_RECLAIM_CLEAN;
cond_resched();
@@ -758,7 +760,9 @@
wait_on_page_writeback(page);
}
- references = page_check_references(page, sc);
+ if (!force_reclaim)
+ references = page_check_references(page, sc);
+
switch (references) {
case PAGEREF_ACTIVATE:
goto activate_locked;
@@ -788,7 +792,7 @@
* processes. Try to unmap it here.
*/
if (page_mapped(page) && mapping) {
- switch (try_to_unmap(page, TTU_UNMAP)) {
+ switch (try_to_unmap(page, ttu_flags)) {
case SWAP_FAIL:
goto activate_locked;
case SWAP_AGAIN:
@@ -960,6 +964,33 @@
return nr_reclaimed;
}
+unsigned long reclaim_clean_pages_from_list(struct zone *zone,
+ struct list_head *page_list)
+{
+ struct scan_control sc = {
+ .gfp_mask = GFP_KERNEL,
+ .priority = DEF_PRIORITY,
+ .may_unmap = 1,
+ };
+ unsigned long ret, dummy1, dummy2;
+ struct page *page, *next;
+ LIST_HEAD(clean_pages);
+
+ list_for_each_entry_safe(page, next, page_list, lru) {
+ if (page_is_file_cache(page) && !PageDirty(page)) {
+ ClearPageActive(page);
+ list_move(&page->lru, &clean_pages);
+ }
+ }
+
+ ret = shrink_page_list(&clean_pages, zone, &sc,
+ TTU_UNMAP|TTU_IGNORE_ACCESS,
+ &dummy1, &dummy2, true);
+ list_splice(&clean_pages, page_list);
+ __mod_zone_page_state(zone, NR_ISOLATED_FILE, -ret);
+ return ret;
+}
+
/*
* Attempt to remove the specified page from its LRU. Only take this page
* if it is of the appropriate PageActive status. Pages which are being
@@ -1278,8 +1309,8 @@
if (nr_taken == 0)
return 0;
- nr_reclaimed = shrink_page_list(&page_list, zone, sc,
- &nr_dirty, &nr_writeback);
+ nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP,
+ &nr_dirty, &nr_writeback, false);
spin_lock_irq(&zone->lru_lock);