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authorJoonsoo Kim <iamjoonsoo.kim@lge.com>2020-08-11 18:30:40 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-12 10:57:55 -0700
commitb518154e59aab3ad0780a169c5cc84bd4ee4357e (patch)
tree92d138645187878f309ec1e01a873e07b5b015ad /mm/swap.c
parentccc5dc67340c109e624e07e02790e9fbdec900d6 (diff)
mm/vmscan: protect the workingset on anonymous LRU
In current implementation, newly created or swap-in anonymous page is started on active list. Growing active list results in rebalancing active/inactive list so old pages on active list are demoted to inactive list. Hence, the page on active list isn't protected at all. Following is an example of this situation. Assume that 50 hot pages on active list. Numbers denote the number of pages on active/inactive list (active | inactive). 1. 50 hot pages on active list 50(h) | 0 2. workload: 50 newly created (used-once) pages 50(uo) | 50(h) 3. workload: another 50 newly created (used-once) pages 50(uo) | 50(uo), swap-out 50(h) This patch tries to fix this issue. Like as file LRU, newly created or swap-in anonymous pages will be inserted to the inactive list. They are promoted to active list if enough reference happens. This simple modification changes the above example as following. 1. 50 hot pages on active list 50(h) | 0 2. workload: 50 newly created (used-once) pages 50(h) | 50(uo) 3. workload: another 50 newly created (used-once) pages 50(h) | 50(uo), swap-out 50(uo) As you can see, hot pages on active list would be protected. Note that, this implementation has a drawback that the page cannot be promoted and will be swapped-out if re-access interval is greater than the size of inactive list but less than the size of total(active+inactive). To solve this potential issue, following patch will apply workingset detection similar to the one that's already applied to file LRU. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Hugh Dickins <hughd@google.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Link: http://lkml.kernel.org/r/1595490560-15117-3-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/swap.c')
-rw-r--r--mm/swap.c13
1 files changed, 7 insertions, 6 deletions
diff --git a/mm/swap.c b/mm/swap.c
index de257c0a89b1..9285e60c7d6e 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -476,23 +476,24 @@ void lru_cache_add(struct page *page)
EXPORT_SYMBOL(lru_cache_add);
/**
- * lru_cache_add_active_or_unevictable
+ * lru_cache_add_inactive_or_unevictable
* @page: the page to be added to LRU
* @vma: vma in which page is mapped for determining reclaimability
*
- * Place @page on the active or unevictable LRU list, depending on its
+ * Place @page on the inactive or unevictable LRU list, depending on its
* evictability. Note that if the page is not evictable, it goes
* directly back onto it's zone's unevictable list, it does NOT use a
* per cpu pagevec.
*/
-void lru_cache_add_active_or_unevictable(struct page *page,
+void lru_cache_add_inactive_or_unevictable(struct page *page,
struct vm_area_struct *vma)
{
+ bool unevictable;
+
VM_BUG_ON_PAGE(PageLRU(page), page);
- if (likely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) != VM_LOCKED))
- SetPageActive(page);
- else if (!TestSetPageMlocked(page)) {
+ unevictable = (vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) == VM_LOCKED;
+ if (unlikely(unevictable) && !TestSetPageMlocked(page)) {
/*
* We use the irq-unsafe __mod_zone_page_stat because this
* counter is not modified from interrupt context, and the pte