mm, vmscan: move LRU lists to node

This moves the LRU lists from the zone to the node and related data such
as counters, tracing, congestion tracking and writeback tracking.

Unfortunately, due to reclaim and compaction retry logic, it is
necessary to account for the number of LRU pages on both zone and node
logic.  Most reclaim logic is based on the node counters but the retry
logic uses the zone counters which do not distinguish inactive and
active sizes.  It would be possible to leave the LRU counters on a
per-zone basis but it's a heavier calculation across multiple cache
lines that is much more frequent than the retry checks.

Other than the LRU counters, this is mostly a mechanical patch but note
that it introduces a number of anomalies.  For example, the scans are
per-zone but using per-node counters.  We also mark a node as congested
when a zone is congested.  This causes weird problems that are fixed
later but is easier to review.

In the event that there is excessive overhead on 32-bit systems due to
the nodes being on LRU then there are two potential solutions

1. Long-term isolation of highmem pages when reclaim is lowmem

   When pages are skipped, they are immediately added back onto the LRU
   list. If lowmem reclaim persisted for long periods of time, the same
   highmem pages get continually scanned. The idea would be that lowmem
   keeps those pages on a separate list until a reclaim for highmem pages
   arrives that splices the highmem pages back onto the LRU. It potentially
   could be implemented similar to the UNEVICTABLE list.

   That would reduce the skip rate with the potential corner case is that
   highmem pages have to be scanned and reclaimed to free lowmem slab pages.

2. Linear scan lowmem pages if the initial LRU shrink fails

   This will break LRU ordering but may be preferable and faster during
   memory pressure than skipping LRU pages.

Link: http://lkml.kernel.org/r/1467970510-21195-4-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 41 insertions, 27 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index cfa870107abe..d4f5cac0a8c3 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -111,12 +111,9 @@ enum zone_stat_item {
 	/* First 128 byte cacheline (assuming 64 bit words) */
 	NR_FREE_PAGES,
 	NR_ALLOC_BATCH,
-	NR_LRU_BASE,
-	NR_INACTIVE_ANON = NR_LRU_BASE, /* must match order of LRU_[IN]ACTIVE */
-	NR_ACTIVE_ANON,		/*  "     "     "   "       "         */
-	NR_INACTIVE_FILE,	/*  "     "     "   "       "         */
-	NR_ACTIVE_FILE,		/*  "     "     "   "       "         */
-	NR_UNEVICTABLE,		/*  "     "     "   "       "         */
+	NR_ZONE_LRU_BASE, /* Used only for compaction and reclaim retry */
+	NR_ZONE_LRU_ANON = NR_ZONE_LRU_BASE,
+	NR_ZONE_LRU_FILE,
 	NR_MLOCK,		/* mlock()ed pages found and moved off LRU */
 	NR_ANON_PAGES,	/* Mapped anonymous pages */
 	NR_FILE_MAPPED,	/* pagecache pages mapped into pagetables.
@@ -134,12 +131,9 @@ enum zone_stat_item {
 	NR_VMSCAN_WRITE,
 	NR_VMSCAN_IMMEDIATE,	/* Prioritise for reclaim when writeback ends */
 	NR_WRITEBACK_TEMP,	/* Writeback using temporary buffers */
-	NR_ISOLATED_ANON,	/* Temporary isolated pages from anon lru */
-	NR_ISOLATED_FILE,	/* Temporary isolated pages from file lru */
 	NR_SHMEM,		/* shmem pages (included tmpfs/GEM pages) */
 	NR_DIRTIED,		/* page dirtyings since bootup */
 	NR_WRITTEN,		/* page writings since bootup */
-	NR_PAGES_SCANNED,	/* pages scanned since last reclaim */
 #if IS_ENABLED(CONFIG_ZSMALLOC)
 	NR_ZSPAGES,		/* allocated in zsmalloc */
 #endif
@@ -161,6 +155,15 @@ enum zone_stat_item {
 	NR_VM_ZONE_STAT_ITEMS };
 
 enum node_stat_item {
+	NR_LRU_BASE,
+	NR_INACTIVE_ANON = NR_LRU_BASE, /* must match order of LRU_[IN]ACTIVE */
+	NR_ACTIVE_ANON,		/*  "     "     "   "       "         */
+	NR_INACTIVE_FILE,	/*  "     "     "   "       "         */
+	NR_ACTIVE_FILE,		/*  "     "     "   "       "         */
+	NR_UNEVICTABLE,		/*  "     "     "   "       "         */
+	NR_ISOLATED_ANON,	/* Temporary isolated pages from anon lru */
+	NR_ISOLATED_FILE,	/* Temporary isolated pages from file lru */
+	NR_PAGES_SCANNED,	/* pages scanned since last reclaim */
 	NR_VM_NODE_STAT_ITEMS
 };
 
@@ -219,7 +222,7 @@ struct lruvec {
 	/* Evictions & activations on the inactive file list */
 	atomic_long_t			inactive_age;
 #ifdef CONFIG_MEMCG
-	struct zone			*zone;
+	struct pglist_data *pgdat;
 #endif
 };
 
@@ -357,13 +360,6 @@ struct zone {
 #ifdef CONFIG_NUMA
 	int node;
 #endif
-
-	/*
-	 * The target ratio of ACTIVE_ANON to INACTIVE_ANON pages on
-	 * this zone's LRU.  Maintained by the pageout code.
-	 */
-	unsigned int inactive_ratio;
-
 	struct pglist_data	*zone_pgdat;
 	struct per_cpu_pageset __percpu *pageset;
 
@@ -495,9 +491,6 @@ struct zone {
 
 	/* Write-intensive fields used by page reclaim */
 
-	/* Fields commonly accessed by the page reclaim scanner */
-	struct lruvec		lruvec;
-
 	/*
 	 * When free pages are below this point, additional steps are taken
 	 * when reading the number of free pages to avoid per-cpu counter
@@ -537,17 +530,20 @@ struct zone {
 
 enum zone_flags {
 	ZONE_RECLAIM_LOCKED,		/* prevents concurrent reclaim */
-	ZONE_CONGESTED,			/* zone has many dirty pages backed by
+	ZONE_FAIR_DEPLETED,		/* fair zone policy batch depleted */
+};
+
+enum pgdat_flags {
+	PGDAT_CONGESTED,		/* pgdat has many dirty pages backed by
 					 * a congested BDI
 					 */
-	ZONE_DIRTY,			/* reclaim scanning has recently found
+	PGDAT_DIRTY,			/* reclaim scanning has recently found
 					 * many dirty file pages at the tail
 					 * of the LRU.
 					 */
-	ZONE_WRITEBACK,			/* reclaim scanning has recently found
+	PGDAT_WRITEBACK,		/* reclaim scanning has recently found
 					 * many pages under writeback
 					 */
-	ZONE_FAIR_DEPLETED,		/* fair zone policy batch depleted */
 };
 
 static inline unsigned long zone_end_pfn(const struct zone *zone)
@@ -707,6 +703,19 @@ typedef struct pglist_data {
 	unsigned long split_queue_len;
 #endif
 
+	/* Fields commonly accessed by the page reclaim scanner */
+	struct lruvec		lruvec;
+
+	/*
+	 * The target ratio of ACTIVE_ANON to INACTIVE_ANON pages on
+	 * this node's LRU.  Maintained by the pageout code.
+	 */
+	unsigned int inactive_ratio;
+
+	unsigned long		flags;
+
+	ZONE_PADDING(_pad2_)
+
 	/* Per-node vmstats */
 	struct per_cpu_nodestat __percpu *per_cpu_nodestats;
 	atomic_long_t		vm_stat[NR_VM_NODE_STAT_ITEMS];
@@ -728,6 +737,11 @@ static inline spinlock_t *zone_lru_lock(struct zone *zone)
 	return &zone->zone_pgdat->lru_lock;
 }
 
+static inline struct lruvec *zone_lruvec(struct zone *zone)
+{
+	return &zone->zone_pgdat->lruvec;
+}
+
 static inline unsigned long pgdat_end_pfn(pg_data_t *pgdat)
 {
 	return pgdat->node_start_pfn + pgdat->node_spanned_pages;
@@ -779,12 +793,12 @@ extern int init_currently_empty_zone(struct zone *zone, unsigned long start_pfn,
 
 extern void lruvec_init(struct lruvec *lruvec);
 
-static inline struct zone *lruvec_zone(struct lruvec *lruvec)
+static inline struct pglist_data *lruvec_pgdat(struct lruvec *lruvec)
 {
 #ifdef CONFIG_MEMCG
-	return lruvec->zone;
+	return lruvec->pgdat;
 #else
-	return container_of(lruvec, struct zone, lruvec);
+	return container_of(lruvec, struct pglist_data, lruvec);
 #endif
 }