Re: Out of Memory: Killed process 16498 (java).

[Dave Jones <davej@redhat.com>]

On Thu, Jan 19, 2006 at 03:11:45PM -0000, Andy Chittenden wrote:
 > DMA free:20kB min:24kB low:28kB high:36kB active:0kB inactive:0kB
 > present:12740kB pages_scanned:4 all_unreclaimable? yes

Note we only scanned 4 pages before we gave up.
Larry Woodman came up with this patch below that clears all_unreclaimable
when in two places where we've made progress at freeing up some pages
which has helped oom situations for some of our users.

From: Larry Woodman <lwoodman@redhat.com>
Signed-off-by: Dave Jones <davej@redhat.com>

--- linux-2.6/mm/filemap.c~	2005-12-10 01:47:15.000000000 -0500
+++ linux-2.6/mm/filemap.c	2005-12-10 01:47:46.000000000 -0500
@@ -471,11 +471,18 @@ EXPORT_SYMBOL(unlock_page);
  */
 void end_page_writeback(struct page *page)
 {
+	struct zone *zone = page_zone(page);
 	if (!TestClearPageReclaim(page) || rotate_reclaimable_page(page)) {
 		if (!test_clear_page_writeback(page))
 			BUG();
 	}
 	smp_mb__after_clear_bit();
+	if (zone->all_unreclaimable) {
+		spin_lock(&zone->lock);
+		zone->all_unreclaimable = 0;
+		zone->pages_scanned = 0;
+		spin_unlock(&zone->lock);
+	}
 	wake_up_page(page, PG_writeback);
 }
 EXPORT_SYMBOL(end_page_writeback);
--- linux-2.6.15/mm/page_alloc.c~	2006-01-09 13:40:03.000000000 -0500
+++ linux-2.6.15/mm/page_alloc.c	2006-01-09 13:40:50.000000000 -0500
@@ -722,6 +722,11 @@ static void fastcall free_hot_cold_page(
 	if (pcp->count >= pcp->high) {
 		free_pages_bulk(zone, pcp->batch, &pcp->list, 0);
 		pcp->count -= pcp->batch;
+	} else if (zone->all_unreclaimable) {
+		spin_lock(&zone->lock);
+		zone->all_unreclaimable = 0;
+		zone->pages_scanned = 0;
+		spin_unlock(&zone->lock);
 	}
 	local_irq_restore(flags);
 	put_cpu();