thp: use compaction in kswapd for GFP_ATOMIC order > 0

This takes advantage of memory compaction to properly generate pages of
order > 0 if regular page reclaim fails and priority level becomes more
severe and we don't reach the proper watermarks.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 72cba40..dfa2ed4 100644 (file)
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -11,6 +11,9 @@
 /* The full zone was compacted */
 #define COMPACT_COMPLETE       3
 
+#define COMPACT_MODE_DIRECT_RECLAIM    0
+#define COMPACT_MODE_KSWAPD            1
+
 #ifdef CONFIG_COMPACTION
 extern int sysctl_compact_memory;
 extern int sysctl_compaction_handler(struct ctl_table *table, int write,
@@ -25,7 +28,8 @@ extern unsigned long try_to_compact_pages(struct zonelist *zonelist,
                        bool sync);
 extern unsigned long compaction_suitable(struct zone *zone, int order);
 extern unsigned long compact_zone_order(struct zone *zone, int order,
-                                               gfp_t gfp_mask, bool sync);
+                                       gfp_t gfp_mask, bool sync,
+                                       int compact_mode);
 
 /* Do not skip compaction more than 64 times */
 #define COMPACT_MAX_DEFER_SHIFT 6
@@ -70,9 +74,10 @@ static inline unsigned long compaction_suitable(struct zone *zone, int order)
 }
 
 static inline unsigned long compact_zone_order(struct zone *zone, int order,
-                                               gfp_t gfp_mask, bool sync)
+                                              gfp_t gfp_mask, bool sync,
+                                              int compact_mode)
 {
-       return 0;
+       return COMPACT_CONTINUE;
 }
 
 static inline void defer_compaction(struct zone *zone)

diff --git a/mm/compaction.c b/mm/compaction.c
index da25b5a..60d52a7 100644 (file)
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -42,6 +42,8 @@ struct compact_control {
        unsigned int order;             /* order a direct compactor needs */
        int migratetype;                /* MOVABLE, RECLAIMABLE etc */
        struct zone *zone;
+
+       int compact_mode;
 };
 
 static unsigned long release_freepages(struct list_head *freelist)
@@ -382,10 +384,10 @@ static void update_nr_listpages(struct compact_control *cc)
 }
 
 static int compact_finished(struct zone *zone,
-                                               struct compact_control *cc)
+                           struct compact_control *cc)
 {
        unsigned int order;
-       unsigned long watermark = low_wmark_pages(zone) + (1 << cc->order);
+       unsigned long watermark;
 
        if (fatal_signal_pending(current))
                return COMPACT_PARTIAL;
@@ -395,12 +397,27 @@ static int compact_finished(struct zone *zone,
                return COMPACT_COMPLETE;
 
        /* Compaction run is not finished if the watermark is not met */
+       if (cc->compact_mode != COMPACT_MODE_KSWAPD)
+               watermark = low_wmark_pages(zone);
+       else
+               watermark = high_wmark_pages(zone);
+       watermark += (1 << cc->order);
+
        if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
                return COMPACT_CONTINUE;
 
        if (cc->order == -1)
                return COMPACT_CONTINUE;
 
+       /*
+        * Generating only one page of the right order is not enough
+        * for kswapd, we must continue until we're above the high
+        * watermark as a pool for high order GFP_ATOMIC allocations
+        * too.
+        */
+       if (cc->compact_mode == COMPACT_MODE_KSWAPD)
+               return COMPACT_CONTINUE;
+
        /* Direct compactor: Is a suitable page free? */
        for (order = cc->order; order < MAX_ORDER; order++) {
                /* Job done if page is free of the right migratetype */
@@ -514,8 +531,9 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
 }
 
 unsigned long compact_zone_order(struct zone *zone,
-                                               int order, gfp_t gfp_mask,
-                                               bool sync)
+                                int order, gfp_t gfp_mask,
+                                bool sync,
+                                int compact_mode)
 {
        struct compact_control cc = {
                .nr_freepages = 0,
@@ -524,6 +542,7 @@ unsigned long compact_zone_order(struct zone *zone,
                .migratetype = allocflags_to_migratetype(gfp_mask),
                .zone = zone,
                .sync = sync,
+               .compact_mode = compact_mode,
        };
        INIT_LIST_HEAD(&cc.freepages);
        INIT_LIST_HEAD(&cc.migratepages);
@@ -569,7 +588,8 @@ unsigned long try_to_compact_pages(struct zonelist *zonelist,
                                                                nodemask) {
                int status;
 
-               status = compact_zone_order(zone, order, gfp_mask, sync);
+               status = compact_zone_order(zone, order, gfp_mask, sync,
+                                           COMPACT_MODE_DIRECT_RECLAIM);
                rc = max(status, rc);
 
                /* If a normal allocation would succeed, stop compacting */
@@ -600,6 +620,7 @@ static int compact_node(int nid)
                        .nr_freepages = 0,
                        .nr_migratepages = 0,
                        .order = -1,
+                       .compact_mode = COMPACT_MODE_DIRECT_RECLAIM,
                };
 
                zone = &pgdat->node_zones[zoneid];

diff --git a/mm/vmscan.c b/mm/vmscan.c
index cfdef0b..f5b762a 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -41,6 +41,7 @@
 #include <linux/memcontrol.h>
 #include <linux/delayacct.h>
 #include <linux/sysctl.h>
+#include <linux/compaction.h>
 
 #include <asm/tlbflush.h>
 #include <asm/div64.h>
@@ -2382,6 +2383,7 @@ loop_again:
                 * cause too much scanning of the lower zones.
                 */
                for (i = 0; i <= end_zone; i++) {
+                       int compaction;
                        struct zone *zone = pgdat->node_zones + i;
                        int nr_slab;
 
@@ -2411,9 +2413,26 @@ loop_again:
                                                lru_pages);
                        sc.nr_reclaimed += reclaim_state->reclaimed_slab;
                        total_scanned += sc.nr_scanned;
+
+                       compaction = 0;
+                       if (order &&
+                           zone_watermark_ok(zone, 0,
+                                              high_wmark_pages(zone),
+                                             end_zone, 0) &&
+                           !zone_watermark_ok(zone, order,
+                                              high_wmark_pages(zone),
+                                              end_zone, 0)) {
+                               compact_zone_order(zone,
+                                                  order,
+                                                  sc.gfp_mask, false,
+                                                  COMPACT_MODE_KSWAPD);
+                               compaction = 1;
+                       }
+
                        if (zone->all_unreclaimable)
                                continue;
-                       if (nr_slab == 0 && !zone_reclaimable(zone))
+                       if (!compaction && nr_slab == 0 &&
+                           !zone_reclaimable(zone))
                                zone->all_unreclaimable = 1;
                        /*
                         * If we've done a decent amount of scanning and
@@ -2424,15 +2443,6 @@ loop_again:
                            total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
                                sc.may_writepage = 1;
 
-                       /*
-                        * Compact the zone for higher orders to reduce
-                        * latencies for higher-order allocations that
-                        * would ordinarily call try_to_compact_pages()
-                        */
-                       if (sc.order > PAGE_ALLOC_COSTLY_ORDER)
-                               compact_zone_order(zone, sc.order, sc.gfp_mask,
-                                                       false);
-
                        if (!zone_watermark_ok_safe(zone, order,
                                        high_wmark_pages(zone), end_zone, 0)) {
                                all_zones_ok = 0;