memcg: oom kill disable and oom status

This adds a feature to disable oom-killer for memcg, if disabled, of
course, tasks under memcg will stop.

But now, we have oom-notifier for memcg.  And the world around memcg is
not under out-of-memory.  memcg's out-of-memory just shows memcg hits
limit.  Then, administrator or management daemon can recover the situation
by

	- kill some process
	- enlarge limit, add more swap.
	- migrate some tasks
	- remove file cache on tmps (difficult ?)

Unlike oom-killer, you can take enough information before killing tasks.
(by gcore, or, ps etc.)

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 94 insertions, 19 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index da2ed3913316..53eb30ebdb49 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -214,6 +214,8 @@ struct mem_cgroup {
         atomic_t        refcnt;
 
         unsigned int    swappiness;
+        /* OOM-Killer disable */
+        int             oom_kill_disable;
 
         /* set when res.limit == memsw.limit */
         bool            memsw_is_minimum;
@@ -235,7 +237,6 @@ struct mem_cgroup {
          * mem_cgroup ? And what type of charges should we move ?
          */
         unsigned long   move_charge_at_immigrate;
-
         /*
          * percpu counter.
          */
@@ -1342,20 +1343,26 @@ static void memcg_wakeup_oom(struct mem_cgroup *mem)
         __wake_up(&memcg_oom_waitq, TASK_NORMAL, 0, mem);
 }
 
+static void memcg_oom_recover(struct mem_cgroup *mem)
+{
+        if (mem->oom_kill_disable && atomic_read(&mem->oom_lock))
+                memcg_wakeup_oom(mem);
+}
+
 /*
  * try to call OOM killer. returns false if we should exit memory-reclaim loop.
  */
 bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask)
 {
         struct oom_wait_info owait;
-        bool locked;
+        bool locked, need_to_kill;
 
         owait.mem = mem;
         owait.wait.flags = 0;
         owait.wait.func = memcg_oom_wake_function;
         owait.wait.private = current;
         INIT_LIST_HEAD(&owait.wait.task_list);
-
+        need_to_kill = true;
         /* At first, try to OOM lock hierarchy under mem.*/
         mutex_lock(&memcg_oom_mutex);
         locked = mem_cgroup_oom_lock(mem);
@@ -1364,15 +1371,17 @@ bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask)
          * accounting. So, UNINTERRUPTIBLE is appropriate. But SIGKILL
          * under OOM is always welcomed, use TASK_KILLABLE here.
          */
-        if (!locked)
-                prepare_to_wait(&memcg_oom_waitq, &owait.wait, TASK_KILLABLE);
-        else
+        prepare_to_wait(&memcg_oom_waitq, &owait.wait, TASK_KILLABLE);
+        if (!locked || mem->oom_kill_disable)
+                need_to_kill = false;
+        if (locked)
                 mem_cgroup_oom_notify(mem);
         mutex_unlock(&memcg_oom_mutex);
 
-        if (locked)
+        if (need_to_kill) {
+                finish_wait(&memcg_oom_waitq, &owait.wait);
                 mem_cgroup_out_of_memory(mem, mask);
-        else {
+        } else {
                 schedule();
                 finish_wait(&memcg_oom_waitq, &owait.wait);
         }
@@ -2162,15 +2171,6 @@ __do_uncharge(struct mem_cgroup *mem, const enum charge_type ctype)
         /* If swapout, usage of swap doesn't decrease */
         if (!do_swap_account || ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT)
                 uncharge_memsw = false;
-        /*
-         * do_batch > 0 when unmapping pages or inode invalidate/truncate.
-         * In those cases, all pages freed continously can be expected to be in
-         * the same cgroup and we have chance to coalesce uncharges.
-         * But we do uncharge one by one if this is killed by OOM(TIF_MEMDIE)
-         * because we want to do uncharge as soon as possible.
-         */
-        if (!current->memcg_batch.do_batch || test_thread_flag(TIF_MEMDIE))
-                goto direct_uncharge;
 
         batch = &current->memcg_batch;
         /*
@@ -2181,6 +2181,17 @@ __do_uncharge(struct mem_cgroup *mem, const enum charge_type ctype)
         if (!batch->memcg)
                 batch->memcg = mem;
         /*
+         * do_batch > 0 when unmapping pages or inode invalidate/truncate.
+         * In those cases, all pages freed continously can be expected to be in
+         * the same cgroup and we have chance to coalesce uncharges.
+         * But we do uncharge one by one if this is killed by OOM(TIF_MEMDIE)
+         * because we want to do uncharge as soon as possible.
+         */
+
+        if (!batch->do_batch || test_thread_flag(TIF_MEMDIE))
+                goto direct_uncharge;
+
+        /*
          * In typical case, batch->memcg == mem. This means we can
          * merge a series of uncharges to an uncharge of res_counter.
          * If not, we uncharge res_counter ony by one.
@@ -2196,6 +2207,8 @@ direct_uncharge:
         res_counter_uncharge(&mem->res, PAGE_SIZE);
         if (uncharge_memsw)
                 res_counter_uncharge(&mem->memsw, PAGE_SIZE);
+        if (unlikely(batch->memcg != mem))
+                memcg_oom_recover(mem);
         return;
 }
 
@@ -2332,6 +2345,7 @@ void mem_cgroup_uncharge_end(void)
                 res_counter_uncharge(&batch->memcg->res, batch->bytes);
         if (batch->memsw_bytes)
                 res_counter_uncharge(&batch->memcg->memsw, batch->memsw_bytes);
+        memcg_oom_recover(batch->memcg);
         /* forget this pointer (for sanity check) */
         batch->memcg = NULL;
 }
@@ -2568,10 +2582,11 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
                                 unsigned long long val)
 {
         int retry_count;
-        u64 memswlimit;
+        u64 memswlimit, memlimit;
         int ret = 0;
         int children = mem_cgroup_count_children(memcg);
         u64 curusage, oldusage;
+        int enlarge;
 
         /*
          * For keeping hierarchical_reclaim simple, how long we should retry
@@ -2582,6 +2597,7 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
 
         oldusage = res_counter_read_u64(&memcg->res, RES_USAGE);
 
+        enlarge = 0;
         while (retry_count) {
                 if (signal_pending(current)) {
                         ret = -EINTR;
@@ -2599,6 +2615,11 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
                         mutex_unlock(&set_limit_mutex);
                         break;
                 }
+
+                memlimit = res_counter_read_u64(&memcg->res, RES_LIMIT);
+                if (memlimit < val)
+                        enlarge = 1;
+
                 ret = res_counter_set_limit(&memcg->res, val);
                 if (!ret) {
                         if (memswlimit == val)
@@ -2620,6 +2641,8 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
                 else
                         oldusage = curusage;
         }
+        if (!ret && enlarge)
+                memcg_oom_recover(memcg);
 
         return ret;
 }
@@ -2628,9 +2651,10 @@ static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
                                         unsigned long long val)
 {
         int retry_count;
-        u64 memlimit, oldusage, curusage;
+        u64 memlimit, memswlimit, oldusage, curusage;
         int children = mem_cgroup_count_children(memcg);
         int ret = -EBUSY;
+        int enlarge = 0;
 
         /* see mem_cgroup_resize_res_limit */
         retry_count = children * MEM_CGROUP_RECLAIM_RETRIES;
@@ -2652,6 +2676,9 @@ static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
                         mutex_unlock(&set_limit_mutex);
                         break;
                 }
+                memswlimit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
+                if (memswlimit < val)
+                        enlarge = 1;
                 ret = res_counter_set_limit(&memcg->memsw, val);
                 if (!ret) {
                         if (memlimit == val)
@@ -2674,6 +2701,8 @@ static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
                 else
                         oldusage = curusage;
         }
+        if (!ret && enlarge)
+                memcg_oom_recover(memcg);
         return ret;
 }
 
@@ -2865,6 +2894,7 @@ move_account:
                         if (ret)
                                 break;
                 }
+                memcg_oom_recover(mem);
                 /* it seems parent cgroup doesn't have enough mem */
                 if (ret == -ENOMEM)
                         goto try_to_free;
@@ -3645,6 +3675,46 @@ static int mem_cgroup_oom_unregister_event(struct cgroup *cgrp,
         return 0;
 }
 
+static int mem_cgroup_oom_control_read(struct cgroup *cgrp,
+        struct cftype *cft,  struct cgroup_map_cb *cb)
+{
+        struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
+
+        cb->fill(cb, "oom_kill_disable", mem->oom_kill_disable);
+
+        if (atomic_read(&mem->oom_lock))
+                cb->fill(cb, "under_oom", 1);
+        else
+                cb->fill(cb, "under_oom", 0);
+        return 0;
+}
+
+/*
+ */
+static int mem_cgroup_oom_control_write(struct cgroup *cgrp,
+        struct cftype *cft, u64 val)
+{
+        struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
+        struct mem_cgroup *parent;
+
+        /* cannot set to root cgroup and only 0 and 1 are allowed */
+        if (!cgrp->parent || !((val == 0) || (val == 1)))
+                return -EINVAL;
+
+        parent = mem_cgroup_from_cont(cgrp->parent);
+
+        cgroup_lock();
+        /* oom-kill-disable is a flag for subhierarchy. */
+        if ((parent->use_hierarchy) ||
+            (mem->use_hierarchy && !list_empty(&cgrp->children))) {
+                cgroup_unlock();
+                return -EINVAL;
+        }
+        mem->oom_kill_disable = val;
+        cgroup_unlock();
+        return 0;
+}
+
 static struct cftype mem_cgroup_files[] = {
         {
                 .name = "usage_in_bytes",
@@ -3702,6 +3772,8 @@ static struct cftype mem_cgroup_files[] = {
         },
         {
                 .name = "oom_control",
+                .read_map = mem_cgroup_oom_control_read,
+                .write_u64 = mem_cgroup_oom_control_write,
                 .register_event = mem_cgroup_oom_register_event,
                 .unregister_event = mem_cgroup_oom_unregister_event,
                 .private = MEMFILE_PRIVATE(_OOM_TYPE, OOM_CONTROL),
@@ -3943,6 +4015,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
         } else {
                 parent = mem_cgroup_from_cont(cont->parent);
                 mem->use_hierarchy = parent->use_hierarchy;
+                mem->oom_kill_disable = parent->oom_kill_disable;
         }
 
         if (parent && parent->use_hierarchy) {
@@ -4215,6 +4288,7 @@ static void mem_cgroup_clear_mc(void)
         if (mc.precharge) {
                 __mem_cgroup_cancel_charge(mc.to, mc.precharge);
                 mc.precharge = 0;
+                memcg_oom_recover(mc.to);
         }
         /*
          * we didn't uncharge from mc.from at mem_cgroup_move_account(), so
@@ -4223,6 +4297,7 @@ static void mem_cgroup_clear_mc(void)
         if (mc.moved_charge) {
                 __mem_cgroup_cancel_charge(mc.from, mc.moved_charge);
                 mc.moved_charge = 0;
+                memcg_oom_recover(mc.from);
         }
         /* we must fixup refcnts and charges */
         if (mc.moved_swap) {