memcg: check under limit at shrink_usage
authorDaisuke Nishimura <>
Mon, 22 Sep 2008 20:57:52 +0000 (13:57 -0700)
committerLinus Torvalds <>
Tue, 23 Sep 2008 15:09:14 +0000 (08:09 -0700)
Current memory cgroup(both in mainline and -mm) doesn't account swap
caches as memory(swap cache support is dropped temporarily now).

So try_to_free_mem_cgroup_pages doesn't reflect the count of pages that
have been moved to swap cache.

But this makes mem_cgroup_shrink_usage fail easily if most of the pages
are anon/shmem, and then shmem_getpage returns -ENOMEM and the process
will be killed.

This patch adds res_counter_check_under_limit to avoid these cases.

BTW, even if swap cache support is enabled again, if a process is moved to
another cgroup, which has been just made, between precharge and
shrink_usage in shmem_getpage, shrink_usage may fail just because there is
no pages to reclaim.

So this change would make sense anyway.

Signed-off-by: Daisuke Nishimura <>
Cc: Balbir Singh <>
Cc: Pavel Emelyanov <>
Cc: KAMEZAWA Hiroyuki <>
Cc: Hugh Dickins <>
Signed-off-by: Andrew Morton <>
Signed-off-by: Linus Torvalds <>

index 0f1f7a7..c0500e4 100644 (file)
@@ -806,6 +806,7 @@ int mem_cgroup_shrink_usage(struct mm_struct *mm, gfp_t gfp_mask)
        do {
                progress = try_to_free_mem_cgroup_pages(mem, gfp_mask);
+               progress += res_counter_check_under_limit(&mem->res);
        } while (!progress && --retry);