[PATCH 7/8] Page scanner changes needed to implement per-container scanner

[Pavel Emelianov <xemul@sw.ru>]

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Struct scan_control now carries:
* the RSS container to free pages in;
* pointer to an isolate_pages() function to isolate
  pages needed for the reclamation.

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diff -upr linux-2.6.20.orig/mm/vmscan.c linux-2.6.20-2/mm/vmscan.c
--- linux-2.6.20.orig/mm/vmscan.c	2007-03-06 19:09:50.000000000 +0300
+++ linux-2.6.20-2/mm/vmscan.c	2007-04-09 11:26:06.000000000 +0400
@@ -45,6 +45,8 @@
 
 #include "internal.h"
 
+#include <linux/rss_container.h>
+
 struct scan_control {
 	/* Incremented by the number of inactive pages that were scanned */
 	unsigned long nr_scanned;
@@ -66,6 +68,10 @@ struct scan_control {
 	int swappiness;
 
 	int all_unreclaimable;
+	struct rss_container *cnt;
+	unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
+			unsigned long *scanned, struct zone *zone,
+			struct rss_container *cont, int active);
 };
 
 /*
@@ -654,6 +660,17 @@ static unsigned long isolate_lru_pages(u
 	return nr_taken;
 }
 
+static unsigned long isolate_pages_global(unsigned long nr,
+		struct list_head *dst, unsigned long *scanned,
+		struct zone *z, struct rss_container *cont,
+		int active)
+{
+	if (active)
+		return isolate_lru_pages(nr, &z->active_list, dst, scanned);
+	else
+		return isolate_lru_pages(nr, &z->inactive_list, dst, scanned);
+}
+
 /*
  * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
  * of reclaimed pages
@@ -676,9 +693,9 @@ static unsigned long shrink_inactive_lis
 		unsigned long nr_scan;
 		unsigned long nr_freed;
 
-		nr_taken = isolate_lru_pages(sc->swap_cluster_max,
-					     &zone->inactive_list,
-					     &page_list, &nr_scan);
+		nr_taken = sc->isolate_pages(sc->swap_cluster_max, &page_list,
+				&nr_scan, zone, sc->cnt, 0);
+
 		zone->nr_inactive -= nr_taken;
 		zone->pages_scanned += nr_scan;
 		spin_unlock_irq(&zone->lru_lock);
@@ -822,8 +839,8 @@ force_reclaim_mapped:
 
 	lru_add_drain();
 	spin_lock_irq(&zone->lru_lock);
-	pgmoved = isolate_lru_pages(nr_pages, &zone->active_list,
-				    &l_hold, &pgscanned);
+	pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, zone,
+			sc->cnt, 1);
 	zone->pages_scanned += pgscanned;
 	zone->nr_active -= pgmoved;
 	spin_unlock_irq(&zone->lru_lock);
@@ -1012,7 +1031,9 @@ static unsigned long shrink_zones(int pr
  * holds filesystem locks which prevent writeout this might not work, and the
  * allocation attempt will fail.
  */
-unsigned long try_to_free_pages(struct zone **zones, gfp_t gfp_mask)
+
+static unsigned long do_try_to_free_pages(struct zone **zones, gfp_t gfp_mask,
+		struct scan_control *sc)
 {
 	int priority;
 	int ret = 0;
@@ -1021,13 +1042,6 @@ unsigned long try_to_free_pages(struct z
 	struct reclaim_state *reclaim_state = current->reclaim_state;
 	unsigned long lru_pages = 0;
 	int i;
-	struct scan_control sc = {
-		.gfp_mask = gfp_mask,
-		.may_writepage = !laptop_mode,
-		.swap_cluster_max = SWAP_CLUSTER_MAX,
-		.may_swap = 1,
-		.swappiness = vm_swappiness,
-	};
 
 	count_vm_event(ALLOCSTALL);
 
@@ -1041,17 +1055,18 @@ unsigned long try_to_free_pages(struct z
 	}
 
 	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
-		sc.nr_scanned = 0;
+		sc->nr_scanned = 0;
 		if (!priority)
 			disable_swap_token();
-		nr_reclaimed += shrink_zones(priority, zones, &sc);
-		shrink_slab(sc.nr_scanned, gfp_mask, lru_pages);
+		nr_reclaimed += shrink_zones(priority, zones, sc);
+		if (sc->cnt == NULL)
+			shrink_slab(sc->nr_scanned, gfp_mask, lru_pages);
 		if (reclaim_state) {
 			nr_reclaimed += reclaim_state->reclaimed_slab;
 			reclaim_state->reclaimed_slab = 0;
 		}
-		total_scanned += sc.nr_scanned;
-		if (nr_reclaimed >= sc.swap_cluster_max) {
+		total_scanned += sc->nr_scanned;
+		if (nr_reclaimed >= sc->swap_cluster_max) {
 			ret = 1;
 			goto out;
 		}
@@ -1063,18 +1078,18 @@ unsigned long try_to_free_pages(struct z
 		 * that's undesirable in laptop mode, where we *want* lumpy
 		 * writeout.  So in laptop mode, write out the whole world.
 		 */
-		if (total_scanned > sc.swap_cluster_max +
-					sc.swap_cluster_max / 2) {
+		if (total_scanned > sc->swap_cluster_max +
+					sc->swap_cluster_max / 2) {
 			wakeup_pdflush(laptop_mode ? 0 : total_scanned);
-			sc.may_writepage = 1;
+			sc->may_writepage = 1;
 		}
 
 		/* Take a nap, wait for some writeback to complete */
-		if (sc.nr_scanned && priority < DEF_PRIORITY - 2)
+		if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
 			congestion_wait(WRITE, HZ/10);
 	}
 	/* top priority shrink_caches still had more to do? don't OOM, then */
-	if (!sc.all_unreclaimable)
+	if (!sc->all_unreclaimable)
 		ret = 1;
 out:
 	/*
@@ -1097,6 +1112,21 @@ out:
 	return ret;
 }
 
+unsigned long try_to_free_pages(struct zone **zones, gfp_t gfp_mask)
+{
+	struct scan_control sc = {
+		.gfp_mask = gfp_mask,
+		.may_writepage = !laptop_mode,
+		.swap_cluster_max = SWAP_CLUSTER_MAX,
+		.may_swap = 1,
+		.swappiness = vm_swappiness,
+		.cnt = NULL,
+		.isolate_pages = isolate_pages_global,
+	};
+
+	return do_try_to_free_pages(zones, gfp_mask, &sc);
+}
+
 /*
  * For kswapd, balance_pgdat() will work across all this node's zones until
  * they are all at pages_high.
@@ -1131,6 +1190,8 @@ static unsigned long balance_pgdat(pg_da
 		.may_swap = 1,
 		.swap_cluster_max = SWAP_CLUSTER_MAX,
 		.swappiness = vm_swappiness,
+		.cnt = NULL,
+		.isolate_pages = isolate_pages_global,
 	};
 	/*
 	 * temp_priority is used to remember the scanning priority at which
@@ -1436,6 +1497,8 @@ unsigned long shrink_all_memory(unsigned
 		.swap_cluster_max = nr_pages,
 		.may_writepage = 1,
 		.swappiness = vm_swappiness,
+		.cnt = NULL,
+		.isolate_pages = isolate_pages_global,
 	};
 
 	current->reclaim_state = &reclaim_state;
@@ -1619,6 +1682,8 @@ static int __zone_reclaim(struct zone *z
 					SWAP_CLUSTER_MAX),
 		.gfp_mask = gfp_mask,
 		.swappiness = vm_swappiness,
+		.cnt = NULL,
+		.isolate_pages = isolate_pages_global,
 	};
 	unsigned long slab_reclaimable;