path: root/mm/workingset.c
diff options
authorJohannes Weiner <>2020-06-03 16:03:03 -0700
committerLinus Torvalds <>2020-06-03 20:09:49 -0700
commit314b57fb0460001a090b35ff8be987f2c868ad3c (patch)
treecb07fbe22ae976778c6c982f7831dccc8fbf3c07 /mm/workingset.c
parent264e90cc07f177adec17ee7cc154ddaa132f0b2d (diff)
mm: balance LRU lists based on relative thrashing
Since the LRUs were split into anon and file lists, the VM has been balancing between page cache and anonymous pages based on per-list ratios of scanned vs. rotated pages. In most cases that tips page reclaim towards the list that is easier to reclaim and has the fewest actively used pages, but there are a few problems with it: 1. Refaults and LRU rotations are weighted the same way, even though one costs IO and the other costs a bit of CPU. 2. The less we scan an LRU list based on already observed rotations, the more we increase the sampling interval for new references, and rotations become even more likely on that list. This can enter a death spiral in which we stop looking at one list completely until the other one is all but annihilated by page reclaim. Since commit a528910e12ec ("mm: thrash detection-based file cache sizing") we have refault detection for the page cache. Along with swapin events, they are good indicators of when the file or anon list, respectively, is too small for its workingset and needs to grow. For example, if the page cache is thrashing, the cache pages need more time in memory, while there may be colder pages on the anonymous list. Likewise, if swapped pages are faulting back in, it indicates that we reclaim anonymous pages too aggressively and should back off. Replace LRU rotations with refaults and swapins as the basis for relative reclaim cost of the two LRUs. This will have the VM target list balances that incur the least amount of IO on aggregate. Signed-off-by: Johannes Weiner <> Signed-off-by: Andrew Morton <> Cc: Joonsoo Kim <> Cc: Michal Hocko <> Cc: Minchan Kim <> Cc: Rik van Riel <> Link: Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'mm/workingset.c')
1 files changed, 4 insertions, 0 deletions
diff --git a/mm/workingset.c b/mm/workingset.c
index e69865739539..a6a2a740ed0b 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -365,6 +365,10 @@ void workingset_refault(struct page *page, void *shadow)
/* Page was active prior to eviction */
if (workingset) {
+ /* XXX: Move to lru_cache_add() when it supports new vs putback */
+ spin_lock_irq(&page_pgdat(page)->lru_lock);
+ lru_note_cost(page);
+ spin_unlock_irq(&page_pgdat(page)->lru_lock);
inc_lruvec_state(lruvec, WORKINGSET_RESTORE);