When the application does not exit cleanly (i.e. SIGTERM) we might
end up with some pages in lru_add_pvec, which is ok. With THP
enabled huge pages may also end up on per cpu lru_add_pvecs.
In the systems with a lot of processors we end up with quite a lot
of memory pending for addition to LRU cache - in the worst case
scenario up to CPUS * PAGE_SIZE * PAGEVEC_SIZE, which on machine
with 200+CPUs means GBs in practice.
We are able to reproduce this problem with the following program:
void main() {
{
size_t size = 55 * 1000 * 1000; // smaller than MEM/CPUS
void *p = mmap(NULL, size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS , -1, 0);
if (p != MAP_FAILED)
memset(p, 0, size);
//munmap(p, size); // uncomment to make the problem go away
}
}
When we run it it will leave significant amount of memory on pvecs.
This memory will be not reclaimed if we hit OOM, so when we run
above program in a loop:
$ for i in `seq 100`; do ./a.out; done
many processes (95% in my case) will be killed by OOM.
This patch flushes lru_add_pvecs on compound page arrival making
the problem less severe - kill rate drops to 0%.
Suggested-by: Michal Hocko <mho...@suse.com>
Tested-by: Lukasz Odzioba <lukasz.odzi...@intel.com>
Signed-off-by: Lukasz Odzioba <lukasz.odzi...@intel.com>
---
mm/swap.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/mm/swap.c b/mm/swap.c
index 9591614..3fe4f18 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -391,9 +391,8 @@ static void __lru_cache_add(struct page *page)
struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
get_page(page);
- if (!pagevec_space(pvec))
+ if (!pagevec_add(pvec, page) || PageCompound(page))
__pagevec_lru_add(pvec);
- pagevec_add(pvec, page);
put_cpu_var(lru_add_pvec);
}
--
1.8.3.1
