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Subject[PATCH v5 4.5/7] mm: optimize isolate_lru_pages()
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This patch moves lru checks from __isolate_lru_page() to its callers.

They aren't required on non-lumpy reclaim: all pages are came from right lru.
Pages isolation on memory compaction should skip only unevictable pages.
Thus we need to check page lru only on pages isolation for lumpy-reclaim.

Plus this patch kills mem_cgroup_lru_del() and uses mem_cgroup_lru_del_list()
instead, because now we already have lru list index.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>

add/remove: 0/1 grow/shrink: 2/1 up/down: 101/-164 (-63)
function old new delta
static.isolate_lru_pages 1018 1103 +85
compact_zone 2230 2246 +16
mem_cgroup_lru_del 65 - -65
__isolate_lru_page 287 188 -99
---
include/linux/memcontrol.h | 5 -----
mm/compaction.c | 3 ++-
mm/memcontrol.c | 5 -----
mm/vmscan.c | 38 +++++++++++++++++---------------------
4 files changed, 19 insertions(+), 32 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 4c4b968..8af2a61 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -66,7 +66,6 @@ struct lruvec *mem_cgroup_zone_lruvec(struct zone *, struct mem_cgroup *);
struct lruvec *mem_cgroup_lru_add_list(struct zone *, struct page *,
enum lru_list);
void mem_cgroup_lru_del_list(struct page *, enum lru_list);
-void mem_cgroup_lru_del(struct page *);
struct lruvec *mem_cgroup_lru_move_lists(struct zone *, struct page *,
enum lru_list, enum lru_list);

@@ -259,10 +258,6 @@ static inline void mem_cgroup_lru_del_list(struct page *page, enum lru_list lru)
{
}

-static inline void mem_cgroup_lru_del(struct page *page)
-{
-}
-
static inline struct lruvec *mem_cgroup_lru_move_lists(struct zone *zone,
struct page *page,
enum lru_list from,
diff --git a/mm/compaction.c b/mm/compaction.c
index 5b02dbd..c2e783d 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -358,7 +358,8 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
continue;
}

- if (!PageLRU(page))
+ /* Isolate only evictable pages */
+ if (!PageLRU(page) || PageUnevictable(page))
continue;

/*
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6864f57..6f62621 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1095,11 +1095,6 @@ void mem_cgroup_lru_del_list(struct page *page, enum lru_list lru)
mz->lru_size[lru] -= 1 << compound_order(page);
}

-void mem_cgroup_lru_del(struct page *page)
-{
- mem_cgroup_lru_del_list(page, page_lru(page));
-}
-
/**
* mem_cgroup_lru_move_lists - account for moving a page between lrus
* @zone: zone of the page
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 0966f11..6a13a05 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1030,21 +1030,11 @@ keep_lumpy:
*/
int __isolate_lru_page(struct page *page, isolate_mode_t mode)
{
- int ret = -EINVAL;
-
- /* Only take pages on the LRU. */
- if (!PageLRU(page))
- return ret;
-
- /* Isolate pages only from allowed LRU lists */
- if (!(mode & BIT(page_lru(page))))
- return ret;
+ int ret = -EBUSY;

/* All possible LRU lists must fit into isolation mask area */
BUILD_BUG_ON(LRU_ALL & ~ISOLATE_LRU_MASK);

- ret = -EBUSY;
-
/*
* To minimise LRU disruption, the caller can indicate that it only
* wants to isolate pages it will be able to operate on without
@@ -1143,21 +1133,16 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
prefetchw_prev_lru_page(page, src, flags);

VM_BUG_ON(!PageLRU(page));
+ VM_BUG_ON(page_lru(page) != lru);

- switch (__isolate_lru_page(page, mode)) {
- case 0:
- mem_cgroup_lru_del(page);
+ if (__isolate_lru_page(page, mode) == 0) {
+ mem_cgroup_lru_del_list(page, lru);
list_move(&page->lru, dst);
nr_taken += hpage_nr_pages(page);
- break;
-
- case -EBUSY:
+ } else {
/* else it is being freed elsewhere */
list_move(&page->lru, src);
continue;
-
- default:
- BUG();
}

if (!sc->order || !(sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM))
@@ -1178,6 +1163,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
end_pfn = pfn + (1 << sc->order);
for (; pfn < end_pfn; pfn++) {
struct page *cursor_page;
+ enum lru_list cursor_lru;

/* The target page is in the block, ignore it. */
if (unlikely(pfn == page_pfn))
@@ -1202,10 +1188,19 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
!PageSwapCache(cursor_page))
break;

+ if (!PageLRU(cursor_page))
+ goto skip_free;
+
+ /* Isolate pages only from allowed LRU lists */
+ cursor_lru = page_lru(cursor_page);
+ if (!(mode & BIT(cursor_lru)))
+ goto skip_free;
+
if (__isolate_lru_page(cursor_page, mode) == 0) {
unsigned int isolated_pages;

- mem_cgroup_lru_del(cursor_page);
+ mem_cgroup_lru_del_list(cursor_page,
+ cursor_lru);
list_move(&cursor_page->lru, dst);
isolated_pages = hpage_nr_pages(cursor_page);
nr_taken += isolated_pages;
@@ -1227,6 +1222,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
* track the head status without a
* page pin.
*/
+skip_free:
if (!PageTail(cursor_page) &&
!atomic_read(&cursor_page->_count))
continue;


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