From: Marcelo Tosatti <marcelo.tosatti@cyclades.com>



Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 25-akpm/mm/vmscan.c |   36 ++++++++++++++++++++++++++++++++----
 1 files changed, 32 insertions(+), 4 deletions(-)

diff -puN mm/vmscan.c~vm-swapout-throttling mm/vmscan.c
--- 25/mm/vmscan.c~vm-swapout-throttling	Tue Aug 31 14:32:35 2004
+++ 25-akpm/mm/vmscan.c	Tue Aug 31 14:32:35 2004
@@ -74,6 +74,10 @@ struct scan_control {
 	unsigned int gfp_mask;
 
 	int may_writepage;
+
+	int inflight;
+
+	int throttled; /* how many times have we throttled on VM inflight IO limit */
 };
 
 /*
@@ -246,8 +250,30 @@ static inline int is_page_cache_freeable
 	return page_count(page) - !!PagePrivate(page) == 2;
 }
 
-static int may_write_to_queue(struct backing_dev_info *bdi)
+/*
+ * This function calculates the maximum pinned-for-IO memory
+ * the page eviction threads can generate. If we hit the max,
+ * we throttle taking a nap.
+ *
+ * Returns true if we cant writeout.
+ */
+int vm_eviction_limits(struct scan_control *sc)
+{
+	if (sc->inflight > (totalram_pages * vm_dirty_ratio) / 100) {
+		if (sc->throttled < 5) {
+			blk_congestion_wait(WRITE, HZ/5);
+			sc->throttled++;
+		}
+		return 1;
+	}
+	return 0;
+}
+
+static int may_write_to_queue(struct backing_dev_info *bdi, struct scan_control *sc)
 {
+	if (vm_eviction_limits(sc)) /* Check VM writeout limit */
+		return 0;
+
 	if (current_is_kswapd())
 		return 1;
 	if (current_is_pdflush())	/* This is unlikely, but why not... */
@@ -287,7 +313,7 @@ static void handle_write_error(struct ad
 /*
  * pageout is called by shrink_list() for each dirty page. Calls ->writepage().
  */
-static pageout_t pageout(struct page *page, struct address_space *mapping)
+static pageout_t pageout(struct page *page, struct address_space *mapping, struct scan_control *sc)
 {
 	/*
 	 * If the page is dirty, only perform writeback if that write
@@ -312,7 +338,7 @@ static pageout_t pageout(struct page *pa
 		return PAGE_KEEP;
 	if (mapping->a_ops->writepage == NULL)
 		return PAGE_ACTIVATE;
-	if (!may_write_to_queue(mapping->backing_dev_info))
+	if (!may_write_to_queue(mapping->backing_dev_info, sc))
 		return PAGE_KEEP;
 
 	if (clear_page_dirty_for_io(page)) {
@@ -422,7 +448,7 @@ static int shrink_list(struct list_head 
 				goto keep_locked;
 
 			/* Page is dirty, try to write it out here */
-			switch(pageout(page, mapping)) {
+			switch (pageout(page, mapping, sc)) {
 			case PAGE_KEEP:
 				goto keep_locked;
 			case PAGE_ACTIVATE:
@@ -813,6 +839,7 @@ shrink_zone(struct zone *zone, struct sc
 		nr_inactive = 0;
 
 	sc->nr_to_reclaim = SWAP_CLUSTER_MAX;
+	sc->throttled = 0;
 
 	while (nr_active || nr_inactive) {
 		if (nr_active) {
@@ -825,6 +852,7 @@ shrink_zone(struct zone *zone, struct sc
 		if (nr_inactive) {
 			sc->nr_to_scan = min(nr_inactive,
 					(unsigned long)SWAP_CLUSTER_MAX);
+			sc->inflight = read_page_state(nr_writeback);
 			nr_inactive -= sc->nr_to_scan;
 			shrink_cache(zone, sc);
 			if (sc->nr_to_reclaim <= 0)
_