The patch titled
Subject: mm,ksm: fix endless looping in allocating memory when ksm enable
has been added to the -mm tree. Its filename is
mmksm-fix-endless-looping-in-allocating-memory-when-ksm-enable.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mmksm-fix-endless-looping-in-allocating-memory-when-ksm-enable.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mmksm-fix-endless-looping-in-allocating-memory-when-ksm-enable.patch
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From: zhong jiang <zhongjiang@xxxxxxxxxx>
Subject: mm,ksm: fix endless looping in allocating memory when ksm enable
I hit the following issue when run a OOM case of the LTP and ksm enable.
Call trace:
[<ffffffc000086a88>] __switch_to+0x74/0x8c
[<ffffffc000a1bae0>] __schedule+0x23c/0x7bc
[<ffffffc000a1c09c>] schedule+0x3c/0x94
[<ffffffc000a1eb84>] rwsem_down_write_failed+0x214/0x350
[<ffffffc000a1e32c>] down_write+0x64/0x80
[<ffffffc00021f794>] __ksm_exit+0x90/0x19c
[<ffffffc0000be650>] mmput+0x118/0x11c
[<ffffffc0000c3ec4>] do_exit+0x2dc/0xa74
[<ffffffc0000c46f8>] do_group_exit+0x4c/0xe4
[<ffffffc0000d0f34>] get_signal+0x444/0x5e0
[<ffffffc000089fcc>] do_signal+0x1d8/0x450
[<ffffffc00008a35c>] do_notify_resume+0x70/0x78
it will lead to a hung task because the exiting task cannot get the mmap
sem for write. but the root cause is that the ksmd holds it for read
while allocateing memory which just takes ages to complete. and ksmd will
loop in the following path.
scan_get_next_rmap_item
down_read
get_next_rmap_item
alloc_rmap_item #ksmd will loop permanently.
we fix it by changing the GFP to allow the allocation sometimes fail, and
we're not at all interested in hearing abot that.
Link: http://lkml.kernel.org/r/1474165570-44398-1-git-send-email-zhongjiang@xxxxxxxxxx
Signed-off-by: zhong jiang <zhongjiang@xxxxxxxxxx>
Suggested-by: Hugh Dickins <hughd@xxxxxxxxxx>
Suggested-by: Michal Hocko <mhocko@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/ksm.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff -puN mm/ksm.c~mmksm-fix-endless-looping-in-allocating-memory-when-ksm-enable mm/ksm.c
--- a/mm/ksm.c~mmksm-fix-endless-looping-in-allocating-memory-when-ksm-enable
+++ a/mm/ksm.c
@@ -283,7 +283,8 @@ static inline struct rmap_item *alloc_rm
{
struct rmap_item *rmap_item;
- rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL);
+ rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL |
+ __GFP_NORETRY | __GFP_NOWARN);
if (rmap_item)
ksm_rmap_items++;
return rmap_item;
_
Patches currently in -mm which might be from zhongjiang@xxxxxxxxxx are
mmksm-fix-endless-looping-in-allocating-memory-when-ksm-enable.patch
mm-page_owner-align-with-pageblock_nr-pages.patch
mm-walk-the-zone-in-pageblock_nr_pages-steps.patch
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