[PATCH] mm: set per-cpu-pages lower threshold to zero

Set the low water mark for hot pages in pcp to zero.

(akpm: for the life of me I cannot remember why we created pcp->low.  Neither
can Martin and the changelog is silent.  Maybe it was just a brainfart, but I
have this feeling that there was a reason.  If not, we should remove the
fields completely.  We'll see.)

Signed-off-by: Rohit Seth <rohit.seth@intel.com>
Cc: <linux-mm@kvack.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

mm/page_alloc.c

@@ -1755,7 +1755,7 @@ inline void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
 
 	pcp = &p->pcp[0];		/* hot */
 	pcp->count = 0;
-	pcp->low = 2 * batch;
+	pcp->low = 0;
 	pcp->high = 6 * batch;
 	pcp->batch = max(1UL, 1 * batch);
 	INIT_LIST_HEAD(&pcp->list);
@@ -1764,7 +1764,7 @@ inline void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
 	pcp->count = 0;
 	pcp->low = 0;
 	pcp->high = 2 * batch;
-	pcp->batch = max(1UL, 1 * batch);
+	pcp->batch = max(1UL, batch/2);
 	INIT_LIST_HEAD(&pcp->list);
 }