mm: memcontrol: simplify detecting when the memory+swap limit is hit

When attempting to charge pages, we first charge the memory counter and
then the memory+swap counter.  If one of the counters is at its limit, we
enter reclaim, but if it's the memory+swap counter, reclaim shouldn't swap
because that wouldn't change the situation.  However, if the counters have
the same limits, we never get to the memory+swap limit.  To know whether
reclaim should swap or not, there is a state flag that indicates whether
the limits are equal and whether hitting the memory limit implies hitting
the memory+swap limit.

Just try the memory+swap counter first.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Dave Hansen <dave@sr71.net>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index fff511e25bb2e68bb7bafbbb1383cd8832097bcd..9cda99dfac4f202a9bc69e4923245ee698ff842a 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -318,9 +318,6 @@ struct mem_cgroup {
        /* OOM-Killer disable */
        int             oom_kill_disable;
 
-       /* set when res.limit == memsw.limit */
-       bool            memsw_is_minimum;
-
        /* protect arrays of thresholds */
        struct mutex thresholds_lock;
 
@@ -1818,8 +1815,6 @@ static unsigned long mem_cgroup_reclaim(struct mem_cgroup *memcg,
 
        if (flags & MEM_CGROUP_RECLAIM_NOSWAP)
                noswap = true;
-       if (!(flags & MEM_CGROUP_RECLAIM_SHRINK) && memcg->memsw_is_minimum)
-               noswap = true;
 
        for (loop = 0; loop < MEM_CGROUP_MAX_RECLAIM_LOOPS; loop++) {
                if (loop)
@@ -2557,16 +2552,17 @@ retry:
                goto done;
 
        size = batch * PAGE_SIZE;
-       if (!res_counter_charge(&memcg->res, size, &fail_res)) {
-               if (!do_swap_account)
+       if (!do_swap_account ||
+           !res_counter_charge(&memcg->memsw, size, &fail_res)) {
+               if (!res_counter_charge(&memcg->res, size, &fail_res))
                        goto done_restock;
-               if (!res_counter_charge(&memcg->memsw, size, &fail_res))
-                       goto done_restock;
-               res_counter_uncharge(&memcg->res, size);
+               if (do_swap_account)
+                       res_counter_uncharge(&memcg->memsw, size);
+               mem_over_limit = mem_cgroup_from_res_counter(fail_res, res);
+       } else {
                mem_over_limit = mem_cgroup_from_res_counter(fail_res, memsw);
                flags |= MEM_CGROUP_RECLAIM_NOSWAP;
-       } else
-               mem_over_limit = mem_cgroup_from_res_counter(fail_res, res);
+       }
 
        if (batch > nr_pages) {
                batch = nr_pages;
@@ -3629,7 +3625,6 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
                                unsigned long long val)
 {
        int retry_count;
-       u64 memswlimit, memlimit;
        int ret = 0;
        int children = mem_cgroup_count_children(memcg);
        u64 curusage, oldusage;
@@ -3656,24 +3651,16 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
                 * We have to guarantee memcg->res.limit <= memcg->memsw.limit.
                 */
                mutex_lock(&set_limit_mutex);
-               memswlimit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
-               if (memswlimit < val) {
+               if (res_counter_read_u64(&memcg->memsw, RES_LIMIT) < val) {
                        ret = -EINVAL;
                        mutex_unlock(&set_limit_mutex);
                        break;
                }
 
-               memlimit = res_counter_read_u64(&memcg->res, RES_LIMIT);
-               if (memlimit < val)
+               if (res_counter_read_u64(&memcg->res, RES_LIMIT) < val)
                        enlarge = 1;
 
                ret = res_counter_set_limit(&memcg->res, val);
-               if (!ret) {
-                       if (memswlimit == val)
-                               memcg->memsw_is_minimum = true;
-                       else
-                               memcg->memsw_is_minimum = false;
-               }
                mutex_unlock(&set_limit_mutex);
 
                if (!ret)
@@ -3698,7 +3685,7 @@ static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
                                        unsigned long long val)
 {
        int retry_count;
-       u64 memlimit, memswlimit, oldusage, curusage;
+       u64 oldusage, curusage;
        int children = mem_cgroup_count_children(memcg);
        int ret = -EBUSY;
        int enlarge = 0;
@@ -3717,22 +3704,14 @@ static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
                 * We have to guarantee memcg->res.limit <= memcg->memsw.limit.
                 */
                mutex_lock(&set_limit_mutex);
-               memlimit = res_counter_read_u64(&memcg->res, RES_LIMIT);
-               if (memlimit > val) {
+               if (res_counter_read_u64(&memcg->res, RES_LIMIT) > val) {
                        ret = -EINVAL;
                        mutex_unlock(&set_limit_mutex);
                        break;
                }
-               memswlimit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
-               if (memswlimit < val)
+               if (res_counter_read_u64(&memcg->memsw, RES_LIMIT) < val)
                        enlarge = 1;
                ret = res_counter_set_limit(&memcg->memsw, val);
-               if (!ret) {
-                       if (memlimit == val)
-                               memcg->memsw_is_minimum = true;
-                       else
-                               memcg->memsw_is_minimum = false;
-               }
                mutex_unlock(&set_limit_mutex);
 
                if (!ret)