Because of the batching logic in shrink_zone() it turns out that the
high-level `priority' variable is not a reliable indicator of the amount of
scanning stress.

This is because with small inactive lists, `priority' can pass through quite
a number of decrements before we do _any_ scanning at all: instead, we've
simply been increasing the value of zone->nr_inactive_scan, waiting for it to
exceed SWAP_CLUSTER_MAX, at which point we do some scanning for real.

So the patch stops using `priority' as a measure of scanning distress and uses

	(total pages scanned) / (total pages reclaimed)

instead.  The code at present fairly arbitrarily decides that if this exceeds
1.5, reclaim is struggling and we need to throttle.


---

 25-akpm/mm/vmscan.c |   17 +++++++++--------
 1 files changed, 9 insertions(+), 8 deletions(-)

diff -puN mm/vmscan.c~vmscan-less-sleepiness mm/vmscan.c
--- 25/mm/vmscan.c~vmscan-less-sleepiness	2004-03-25 22:25:48.367046584 -0800
+++ 25-akpm/mm/vmscan.c	2004-03-25 22:27:34.007986720 -0800
@@ -876,11 +876,9 @@ int try_to_free_pages(struct zone **zone
 		if (total_scanned > SWAP_CLUSTER_MAX + SWAP_CLUSTER_MAX/2) {
 			wakeup_bdflush(laptop_mode ? 0 : total_scanned);
 			do_writepage = 1;
+			blk_congestion_wait(WRITE, HZ/10);
 		}
 
-		/* Take a nap, wait for some writeback to complete */
-		if (scanned && priority < DEF_PRIORITY - 2)
-			blk_congestion_wait(WRITE, HZ/10);
 	}
 	if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY))
 		out_of_memory();
@@ -1009,12 +1007,15 @@ scan:
 			continue;	/* swsusp: need to do more work */
 		if (all_zones_ok)
 			break;		/* kswapd: all done */
-		/*
-		 * OK, kswapd is getting into trouble.  Take a nap, then take
-		 * another pass across the zones.
-		 */
-		if (total_scanned && priority < DEF_PRIORITY - 2)
+		if (do_writepage) {
+			/*
+			 * OK, kswapd is getting into trouble.  Take a nap,
+			 * then take another pass across the zones.  We reuse
+			 * do_writepage here, just because it happens to be
+			 * exactly what we want...
+			 */
 			blk_congestion_wait(WRITE, HZ/10);
+		}
 	}
 out:
 	for (i = 0; i < pgdat->nr_zones; i++) {

_