This is a note to let you know that I've just added the patch titled
mm: vmscan: forcibly scan highmem if there are too many buffer_heads
pinning highmem
to the 3.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-vmscan-forcibly-scan-highmem-if-there-are-too-many-buffer_heads-pinning-highmem.patch
and it can be found in the queue-3.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From cc715d99e529d470dde2f33a6614f255adea71f3 Mon Sep 17 00:00:00 2001
From: Mel Gorman <[email protected]>
Date: Wed, 21 Mar 2012 16:34:00 -0700
Subject: mm: vmscan: forcibly scan highmem if there are too many buffer_heads
pinning highmem
From: Mel Gorman <[email protected]>
commit cc715d99e529d470dde2f33a6614f255adea71f3 upstream.
Stuart Foster reported on bugzilla that copying large amounts of data
from NTFS caused an OOM kill on 32-bit X86 with 16G of memory. Andrew
Morton correctly identified that the problem was NTFS was using 512
blocks meaning each page had 8 buffer_heads in low memory pinning it.
In the past, direct reclaim used to scan highmem even if the allocating
process did not specify __GFP_HIGHMEM but not any more. kswapd no longer
will reclaim from zones that are above the high watermark. The intention
in both cases was to minimise unnecessary reclaim. The downside is on
machines with large amounts of highmem that lowmem can be fully consumed
by buffer_heads with nothing trying to free them.
The following patch is based on a suggestion by Andrew Morton to extend
the buffer_heads_over_limit case to force kswapd and direct reclaim to
scan the highmem zone regardless of the allocation request or watermarks.
Addresses https://bugzilla.kernel.org/show_bug.cgi?id=42578
[[email protected]: move buffer_heads_over_limit check up]
[[email protected]: buffer_heads_over_limit is unlikely]
Reported-by: Stuart Foster <[email protected]>
Tested-by: Stuart Foster <[email protected]>
Signed-off-by: Mel Gorman <[email protected]>
Signed-off-by: Hugh Dickins <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Christoph Lameter <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
mm/vmscan.c | 42 +++++++++++++++++++++++++++++-------------
1 file changed, 29 insertions(+), 13 deletions(-)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1643,18 +1643,6 @@ static void move_active_pages_to_lru(str
unsigned long pgmoved = 0;
struct page *page;
- if (buffer_heads_over_limit) {
- spin_unlock_irq(&zone->lru_lock);
- list_for_each_entry(page, list, lru) {
- if (page_has_private(page) && trylock_page(page)) {
- if (page_has_private(page))
- try_to_release_page(page, 0);
- unlock_page(page);
- }
- }
- spin_lock_irq(&zone->lru_lock);
- }
-
while (!list_empty(list)) {
struct lruvec *lruvec;
@@ -1737,6 +1725,14 @@ static void shrink_active_list(unsigned
continue;
}
+ if (unlikely(buffer_heads_over_limit)) {
+ if (page_has_private(page) && trylock_page(page)) {
+ if (page_has_private(page))
+ try_to_release_page(page, 0);
+ unlock_page(page);
+ }
+ }
+
if (page_referenced(page, 0, mz->mem_cgroup, &vm_flags)) {
nr_rotated += hpage_nr_pages(page);
/*
@@ -2235,6 +2231,14 @@ static bool shrink_zones(int priority, s
unsigned long nr_soft_scanned;
bool aborted_reclaim = false;
+ /*
+ * If the number of buffer_heads in the machine exceeds the maximum
+ * allowed level, force direct reclaim to scan the highmem zone as
+ * highmem pages could be pinning lowmem pages storing buffer_heads
+ */
+ if (buffer_heads_over_limit)
+ sc->gfp_mask |= __GFP_HIGHMEM;
+
for_each_zone_zonelist_nodemask(zone, z, zonelist,
gfp_zone(sc->gfp_mask), sc->nodemask) {
if (!populated_zone(zone))
@@ -2724,6 +2728,17 @@ loop_again:
*/
age_active_anon(zone, &sc, priority);
+ /*
+ * If the number of buffer_heads in the machine
+ * exceeds the maximum allowed level and this node
+ * has a highmem zone, force kswapd to reclaim from
+ * it to relieve lowmem pressure.
+ */
+ if (buffer_heads_over_limit && is_highmem_idx(i)) {
+ end_zone = i;
+ break;
+ }
+
if (!zone_watermark_ok_safe(zone, order,
high_wmark_pages(zone), 0, 0)) {
end_zone = i;
@@ -2786,7 +2801,8 @@ loop_again:
(zone->present_pages +
KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
KSWAPD_ZONE_BALANCE_GAP_RATIO);
- if (!zone_watermark_ok_safe(zone, order,
+ if ((buffer_heads_over_limit && is_highmem_idx(i)) ||
+ !zone_watermark_ok_safe(zone, order,
high_wmark_pages(zone) + balance_gap,
end_zone, 0)) {
shrink_zone(priority, zone, &sc);
Patches currently in stable-queue which might be from [email protected] are
queue-3.3/mm-vmscan-forcibly-scan-highmem-if-there-are-too-many-buffer_heads-pinning-highmem.patch
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