path: root/mm/vmscan.c
diff options
authorRik van Riel <riel@redhat.com>2007-10-16 01:24:50 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-16 09:42:54 -0700
commit32a4330d4156e55a4888a201f484dbafed9504ed (patch)
tree1339473dab0fe493dc9feb59833cdf23cf2b1780 /mm/vmscan.c
parentmm: no need to cast vmalloc() return value in zone_wait_table_init() (diff)
mm: prevent kswapd from freeing excessive amounts of lowmem
The current VM can get itself into trouble fairly easily on systems with a small ZONE_HIGHMEM, which is common on i686 computers with 1GB of memory. On one side, page_alloc() will allocate down to zone->pages_low, while on the other side, kswapd() and balance_pgdat() will try to free memory from every zone, until every zone has more free pages than zone->pages_high. Highmem can be filled up to zone->pages_low with page tables, ramfs, vmalloc allocations and other unswappable things quite easily and without many bad side effects, since we still have a huge ZONE_NORMAL to do future allocations from. However, as long as the number of free pages in the highmem zone is below zone->pages_high, kswapd will continue swapping things out from ZONE_NORMAL, too! Sami Farin managed to get his system into a stage where kswapd had freed about 700MB of low memory and was still "going strong". The attached patch will make kswapd stop paging out data from zones when there is more than enough memory free. We do go above zone->pages_high in order to keep pressure between zones equal in normal circumstances, but the patch should prevent the kind of excesses that made Sami's computer totally unusable. Signed-off-by: Rik van Riel <riel@redhat.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to '')
1 files changed, 7 insertions, 1 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index a6e65d024995..bc58802663be 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1371,7 +1371,13 @@ loop_again:
temp_priority[i] = priority;
sc.nr_scanned = 0;
note_zone_scanning_priority(zone, priority);
- nr_reclaimed += shrink_zone(priority, zone, &sc);
+ /*
+ * We put equal pressure on every zone, unless one
+ * zone has way too many pages free already.
+ */
+ if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
+ end_zone, 0))
+ nr_reclaimed += shrink_zone(priority, zone, &sc);
reclaim_state->reclaimed_slab = 0;
nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,