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authorJohannes Weiner <hannes@cmpxchg.org>2014-12-12 16:56:13 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-12-13 12:42:48 -0800
commit6b4f7799c6a5703ac6b8c0649f4c22f00fa07513 (patch)
tree8d8c5f668a5a86bfff6af18e937bec4ea13027b8 /mm/page_alloc.c
parentf5f302e21257ebb0c074bbafc37606c26d28cc3d (diff)
mm: vmscan: invoke slab shrinkers from shrink_zone()
The slab shrinkers are currently invoked from the zonelist walkers in kswapd, direct reclaim, and zone reclaim, all of which roughly gauge the eligible LRU pages and assemble a nodemask to pass to NUMA-aware shrinkers, which then again have to walk over the nodemask. This is redundant code, extra runtime work, and fairly inaccurate when it comes to the estimation of actually scannable LRU pages. The code duplication will only get worse when making the shrinkers cgroup-aware and requiring them to have out-of-band cgroup hierarchy walks as well. Instead, invoke the shrinkers from shrink_zone(), which is where all reclaimers end up, to avoid this duplication. Take the count for eligible LRU pages out of get_scan_count(), which considers many more factors than just the availability of swap space, like zone_reclaimable_pages() currently does. Accumulate the number over all visited lruvecs to get the per-zone value. Some nodes have multiple zones due to memory addressing restrictions. To avoid putting too much pressure on the shrinkers, only invoke them once for each such node, using the class zone of the allocation as the pivot zone. For now, this integrates the slab shrinking better into the reclaim logic and gets rid of duplicative invocations from kswapd, direct reclaim, and zone reclaim. It also prepares for cgroup-awareness, allowing memcg-capable shrinkers to be added at the lruvec level without much duplication of both code and runtime work. This changes kswapd behavior, which used to invoke the shrinkers for each zone, but with scan ratios gathered from the entire node, resulting in meaningless pressure quantities on multi-zone nodes. Zone reclaim behavior also changes. It used to shrink slabs until the same amount of pages were shrunk as were reclaimed from the LRUs. Now it merely invokes the shrinkers once with the zone's scan ratio, which makes the shrinkers go easier on caches that implement aging and would prefer feeding back pressure from recently used slab objects to unused LRU pages. [vdavydov@parallels.com: assure class zone is populated] Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Dave Chinner <david@fromorbit.com> Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r--mm/page_alloc.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c13b6b29add2..9d3870862293 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6284,9 +6284,9 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
if (!PageLRU(page))
found++;
/*
- * If there are RECLAIMABLE pages, we need to check it.
- * But now, memory offline itself doesn't call shrink_slab()
- * and it still to be fixed.
+ * If there are RECLAIMABLE pages, we need to check
+ * it. But now, memory offline itself doesn't call
+ * shrink_node_slabs() and it still to be fixed.
*/
/*
* If the page is not RAM, page_count()should be 0.