Re: lowmem_reserve (replaces protection)

[Andrea Arcangeli <andrea@novell.com>]

this _incremental_ 2/? patch should fix the longtanding kswapd issue
vs protection algorithm, now lowmem_reserve (partly hidden by the lack
of lowmem_reserve/protection or equivalent band-aid enabled in 2.6.9).

--- 2-kswapd-balance/include/linux/mmzone.h.~1~	2004-10-27 03:17:07.207812600 +0200
+++ 2-kswapd-balance/include/linux/mmzone.h	2004-10-27 03:26:22.673369000 +0200
@@ -273,7 +273,7 @@ void __get_zone_counts(unsigned long *ac
 void get_zone_counts(unsigned long *active, unsigned long *inactive,
 			unsigned long *free);
 void build_all_zonelists(void);
-void wakeup_kswapd(struct zone *zone);
+void wakeup_kswapd(struct zone *zone, int classzone_idx);
 
 /*
  * zone_idx() returns 0 for the ZONE_DMA zone, 1 for the ZONE_NORMAL zone, etc.
--- 2-kswapd-balance/mm/page_alloc.c.~1~	2004-10-27 03:17:07.215811384 +0200
+++ 2-kswapd-balance/mm/page_alloc.c	2004-10-27 03:24:31.351292528 +0200
@@ -641,7 +641,7 @@ __alloc_pages(unsigned int gfp_mask, uns
 	}
 
 	for (i = 0; (z = zones[i]) != NULL; i++)
-		wakeup_kswapd(z);
+		wakeup_kswapd(z, classzone_idx);
 
 	/*
 	 * Go through the zonelist again. Let __GFP_HIGH and allocations
--- 2-kswapd-balance/mm/vmscan.c.~1~	2004-10-27 03:14:22.563842288 +0200
+++ 2-kswapd-balance/mm/vmscan.c	2004-10-27 03:26:57.462080312 +0200
@@ -1169,11 +1169,11 @@ static int kswapd(void *p)
 /*
  * A zone is low on free memory, so wake its kswapd task to service it.
  */
-void wakeup_kswapd(struct zone *zone)
+void wakeup_kswapd(struct zone *zone, int classzone_idx)
 {
 	if (zone->present_pages == 0)
 		return;
-	if (zone->free_pages > zone->pages_low)
+	if (zone->free_pages > zone->pages_low + zone->lowmem_reserve[classzone_idx])
 		return;
 	if (!waitqueue_active(&zone->zone_pgdat->kswapd_wait))
 		return;