[PATCH 16 of 16] avoid some lock operation in vm fast path

[Andrea Arcangeli <andrea@suse.de>]

# HG changeset patch
# User Andrea Arcangeli <andrea@suse.de>
# Date 1181332962 -7200
# Node ID 19fb832beb3c83b7bed13c1a2f54ec4e077cfc0d
# Parent  31ef5d0bf924fb47da144321f692f4fefebf5cf5
avoid some lock operation in vm fast path

Let's not bloat the kernel for numa. Not nice, but at least this way
perhaps somebody will clean it up instead of hiding the inefficiency in
there.

Signed-off-by: Andrea Arcangeli <andrea@suse.de>

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -223,8 +223,10 @@ struct zone {
 	unsigned long		pages_scanned;	   /* since last reclaim */
 	int			all_unreclaimable; /* All pages pinned */
 
+#ifdef CONFIG_NUMA
 	/* A count of how many reclaimers are scanning this zone */
 	atomic_t		reclaim_in_progress;
+#endif
 
 	/* Zone statistics */
 	atomic_long_t		vm_stat[NR_VM_ZONE_STAT_ITEMS];
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2650,7 +2650,9 @@ static void __meminit free_area_init_cor
 		INIT_LIST_HEAD(&zone->active_list);
 		INIT_LIST_HEAD(&zone->inactive_list);
 		zap_zone_vm_stats(zone);
+#ifdef CONFIG_NUMA
 		atomic_set(&zone->reclaim_in_progress, 0);
+#endif
 		if (!size)
 			continue;
 
diff --git a/mm/vmscan.c b/mm/vmscan.c
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -909,7 +909,9 @@ static unsigned long shrink_zone(int pri
 	unsigned long nr_to_scan;
 	unsigned long nr_reclaimed = 0;
 
+#ifdef CONFIG_NUMA
 	atomic_inc(&zone->reclaim_in_progress);
+#endif
 
 	/*
 	 * Add one to `nr_to_scan' just to make sure that the kernel will
@@ -945,7 +947,9 @@ static unsigned long shrink_zone(int pri
 
 	throttle_vm_writeout(sc->gfp_mask);
 
+#ifdef CONFIG_NUMA
 	atomic_dec(&zone->reclaim_in_progress);
+#endif
 	return nr_reclaimed;
 }
 

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