Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/include/linux/mmzone.h | 5 +++--
25-akpm/mm/vmscan.c | 27 ++++++++++++++++++++++-----
2 files changed, 25 insertions(+), 7 deletions(-)
diff -puN mm/vmscan.c~no-wild-kswapd-2 mm/vmscan.c
--- 25/mm/vmscan.c~no-wild-kswapd-2 2004-10-07 23:46:22.870851856 -0700
+++ 25-akpm/mm/vmscan.c 2004-10-07 23:46:22.876850944 -0700
@@ -990,6 +990,17 @@ out:
* of the number of free pages in the lower zones. This interoperates with
* the page allocator fallback scheme to ensure that aging of pages is balanced
* across the zones.
+ *
+ * kswapd can be semi-livelocked if some other process is allocating pages
+ * while kswapd is simultaneously trying to balance the same zone. That's OK,
+ * because we _want_ kswapd to work continuously in this situation. But a
+ * side-effect of kswapd's ongoing work is that the pageout priority keeps on
+ * winding up so we bogusly start doing swapout.
+ *
+ * To fix this we take a snapshot of the number of pages which need to be
+ * reclaimed from each zone in zone->pages_to_reclaim and never reclaim more
+ * pages than that. Once the required number of pages have been reclaimed from
+ * each zone, we're done. kwsapd will go back to sleep until someone wakes it.
*/
static int balance_pgdat(pg_data_t *pgdat, int nr_pages)
{
@@ -1010,6 +1021,7 @@ static int balance_pgdat(pg_data_t *pgda
struct zone *zone = pgdat->node_zones + i;
zone->temp_priority = DEF_PRIORITY;
+ zone->pages_to_reclaim = zone->pages_high - zone->free_pages;
}
for (priority = DEF_PRIORITY; priority >= 0; priority--) {
@@ -1032,7 +1044,7 @@ static int balance_pgdat(pg_data_t *pgda
priority != DEF_PRIORITY)
continue;
- if (zone->free_pages <= zone->pages_high) {
+ if (zone->pages_to_reclaim > 0) {
end_zone = i;
break;
}
@@ -1068,10 +1080,11 @@ static int balance_pgdat(pg_data_t *pgda
if (zone->all_unreclaimable && priority != DEF_PRIORITY)
continue;
- if (nr_pages == 0) { /* Not software suspend */
- if (zone->free_pages <= zone->pages_high)
- all_zones_ok = 0;
- }
+ if (zone->pages_to_reclaim <= 0)
+ continue;
+
+ if (nr_pages == 0) /* Not software suspend */
+ all_zones_ok = 0;
zone->temp_priority = priority;
if (zone->prev_priority > priority)
zone->prev_priority = priority;
@@ -1081,6 +1094,10 @@ static int balance_pgdat(pg_data_t *pgda
shrink_zone(zone, &sc);
reclaim_state->reclaimed_slab = 0;
shrink_slab(sc.nr_scanned, GFP_KERNEL, lru_pages);
+
+ /* This fails to account for slab reclaim */
+ zone->pages_to_reclaim -= sc.nr_reclaimed;
+
sc.nr_reclaimed += reclaim_state->reclaimed_slab;
total_reclaimed += sc.nr_reclaimed;
total_scanned += sc.nr_scanned;
diff -puN include/linux/mmzone.h~no-wild-kswapd-2 include/linux/mmzone.h
--- 25/include/linux/mmzone.h~no-wild-kswapd-2 2004-10-07 23:46:22.872851552 -0700
+++ 25-akpm/include/linux/mmzone.h 2004-10-07 23:46:22.877850792 -0700
@@ -137,8 +137,9 @@ struct zone {
unsigned long nr_scan_inactive;
unsigned long nr_active;
unsigned long nr_inactive;
- int all_unreclaimable; /* All pages pinned */
- unsigned long pages_scanned; /* since last reclaim */
+ long pages_to_reclaim; /* kswapd usage */
+ int all_unreclaimable; /* All pages pinned */
+ unsigned long pages_scanned; /* since last reclaim */
ZONE_PADDING(_pad2_)
_