[PATCH] stricter pagecache pruning

[Rik van Riel <H.H.vanRiel@phys.uu.nl>]

Hi,

I hope this patch will alleviate some of Andrea's
problems with the page cache growing out of bounds.

It makes sure that, when the cache uses too much,
shrink_mmap() is called continuously; only the
last thing tried can be something else.

I'd like to hear some results, as I haven't tried
it myself ... It seems obvious enough, so it would
probably be best if it's tried ASAP with as many
different machines/loads as possible.

Rik.
+-------------------------------------------------------------------+
| Linux memory management tour guide.        H.H.vanRiel@phys.uu.nl |
| Scouting Vries cubscout leader.      http://www.phys.uu.nl/~riel/ |
+-------------------------------------------------------------------+
--- linux/mm/vmscan.c.orig	Sat Jul 11 09:13:37 1998
+++ linux/mm/vmscan.c	Sat Jul 11 09:26:18 1998
@@ -448,7 +448,7 @@
 {
 	static int state = 0;
 	int i=6;
-	int stop;
+	int stop, shrink = 0;
 
 	/* Always trim SLAB caches when memory gets low. */
 	kmem_cache_reap(gfp_mask);
@@ -458,14 +458,19 @@
 	if (gfp_mask & __GFP_WAIT)
 		stop = 0;
 	if (((buffermem >> PAGE_SHIFT) * 100 > buffer_mem.borrow_percent * num_physpages)
-		   || (page_cache_size * 100 > page_cache.borrow_percent * num_physpages))
+		   || (page_cache_size * 100 > page_cache.borrow_percent * num_physpages)) {
 		state = 0;
+		shrink = i - stop;
+	}
 
 	switch (state) {
 		do {
 		case 0:
-			if (shrink_mmap(i, gfp_mask))
-				return 1;
+			do {
+				if (shrink_mmap(i, gfp_mask))
+					return 1;
+				if (shrink) shrink--;
+			} while (shrink);
 			state = 1;
 		case 1:
 			if ((gfp_mask & __GFP_IO) && shm_swap(i, gfp_mask))