On Tue, 16 Feb 2010, David Rientjes wrote:
> Ok, I'll eliminate pagefault_out_of_memory() and get it to use
> out_of_memory() by only checking for constrained_alloc() when
> gfp_mask != 0.
>
What do you think about making pagefaults use out_of_memory() directly and
respecting the sysctl_panic_on_oom settings?
This removes the check for a parallel memcg oom killing since we can
guarantee that's not going to happen if we take ZONE_OOM_LOCKED for all
populated zones (nobody is currently executing the oom killer) and no
tasks have TIF_MEMDIE set.
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
---
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -124,7 +124,6 @@ static inline bool mem_cgroup_disabled(void)
return false;
}
-extern bool mem_cgroup_oom_called(struct task_struct *task);
void mem_cgroup_update_file_mapped(struct page *page, int val);
unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
gfp_t gfp_mask, int nid,
@@ -258,11 +257,6 @@ static inline bool mem_cgroup_disabled(void)
return true;
}
-static inline bool mem_cgroup_oom_called(struct task_struct *task)
-{
- return false;
-}
-
static inline int
mem_cgroup_inactive_anon_is_low(struct mem_cgroup *memcg)
{
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -200,7 +200,6 @@ struct mem_cgroup {
* Should the accounting and control be hierarchical, per subtree?
*/
bool use_hierarchy;
- unsigned long last_oom_jiffies;
atomic_t refcnt;
unsigned int swappiness;
@@ -1234,34 +1233,6 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
return total;
}
-bool mem_cgroup_oom_called(struct task_struct *task)
-{
- bool ret = false;
- struct mem_cgroup *mem;
- struct mm_struct *mm;
-
- rcu_read_lock();
- mm = task->mm;
- if (!mm)
- mm = &init_mm;
- mem = mem_cgroup_from_task(rcu_dereference(mm->owner));
- if (mem && time_before(jiffies, mem->last_oom_jiffies + HZ/10))
- ret = true;
- rcu_read_unlock();
- return ret;
-}
-
-static int record_last_oom_cb(struct mem_cgroup *mem, void *data)
-{
- mem->last_oom_jiffies = jiffies;
- return 0;
-}
-
-static void record_last_oom(struct mem_cgroup *mem)
-{
- mem_cgroup_walk_tree(mem, NULL, record_last_oom_cb);
-}
-
/*
* Currently used to update mapped file statistics, but the routine can be
* generalized to update other statistics as well.
@@ -1549,10 +1520,8 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
}
if (!nr_retries--) {
- if (oom) {
+ if (oom)
mem_cgroup_out_of_memory(mem_over_limit, gfp_mask);
- record_last_oom(mem_over_limit);
- }
goto nomem;
}
}
@@ -2408,8 +2377,6 @@ void mem_cgroup_end_migration(struct mem_cgroup *mem,
/*
* A call to try to shrink memory usage on charge failure at shmem's swapin.
- * Calling hierarchical_reclaim is not enough because we should update
- * last_oom_jiffies to prevent pagefault_out_of_memory from invoking global OOM.
* Moreover considering hierarchy, we should reclaim from the mem_over_limit,
* not from the memcg which this page would be charged to.
* try_charge_swapin does all of these works properly.
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -490,29 +490,6 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
return oom_kill_task(victim);
}
-#ifdef CONFIG_CGROUP_MEM_RES_CTLR
-void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
-{
- unsigned long points = 0;
- struct task_struct *p;
-
- read_lock(&tasklist_lock);
-retry:
- p = select_bad_process(&points, mem, CONSTRAINT_NONE, NULL);
- if (PTR_ERR(p) == -1UL)
- goto out;
-
- if (!p)
- p = current;
-
- if (oom_kill_process(p, gfp_mask, 0, points, mem,
- "Memory cgroup out of memory"))
- goto retry;
-out:
- read_unlock(&tasklist_lock);
-}
-#endif
-
static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
int register_oom_notifier(struct notifier_block *nb)
@@ -578,6 +555,70 @@ void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
}
/*
+ * Try to acquire the oom killer lock for all system zones. Returns zero if a
+ * parallel oom killing is taking place, otherwise locks all zones and returns
+ * non-zero.
+ */
+static int try_set_system_oom(void)
+{
+ struct zone *zone;
+ int ret = 1;
+
+ spin_lock(&zone_scan_lock);
+ for_each_populated_zone(zone)
+ if (zone_is_oom_locked(zone)) {
+ ret = 0;
+ goto out;
+ }
+ for_each_populated_zone(zone)
+ zone_set_flag(zone, ZONE_OOM_LOCKED);
+out:
+ spin_unlock(&zone_scan_lock);
+ return ret;
+}
+
+/*
+ * Clears ZONE_OOM_LOCKED for all system zones so that failed allocation
+ * attempts or page faults may now recall the oom killer, if necessary.
+ */
+static void clear_system_oom(void)
+{
+ struct zone *zone;
+
+ spin_lock(&zone_scan_lock);
+ for_each_populated_zone(zone)
+ zone_clear_flag(zone, ZONE_OOM_LOCKED);
+ spin_unlock(&zone_scan_lock);
+}
+
+
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
+{
+ unsigned long points = 0;
+ struct task_struct *p;
+
+ if (!try_set_system_oom())
+ return;
+ read_lock(&tasklist_lock);
+retry:
+ p = select_bad_process(&points, mem, CONSTRAINT_NONE, NULL);
+ if (PTR_ERR(p) == -1UL)
+ goto out;
+
+ if (!p)
+ p = current;
+
+ if (oom_kill_process(p, gfp_mask, 0, points, mem,
+ "Memory cgroup out of memory"))
+ goto retry;
+out:
+ read_unlock(&tasklist_lock);
+ clear_system_oom();
+}
+#endif
+
+/*
* Must be called with tasklist_lock held for read.
*/
static void __out_of_memory(gfp_t gfp_mask, int order,
@@ -612,46 +653,9 @@ retry:
goto retry;
}
-/*
- * pagefault handler calls into here because it is out of memory but
- * doesn't know exactly how or why.
- */
-void pagefault_out_of_memory(void)
-{
- unsigned long freed = 0;
-
- blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
- if (freed > 0)
- /* Got some memory back in the last second. */
- return;
-
- /*
- * If this is from memcg, oom-killer is already invoked.
- * and not worth to go system-wide-oom.
- */
- if (mem_cgroup_oom_called(current))
- goto rest_and_return;
-
- if (sysctl_panic_on_oom)
- panic("out of memory from page fault. panic_on_oom is selected.\n");
-
- read_lock(&tasklist_lock);
- /* unknown gfp_mask and order */
- __out_of_memory(0, 0, CONSTRAINT_NONE, NULL);
- read_unlock(&tasklist_lock);
-
- /*
- * Give "p" a good chance of killing itself before we
- * retry to allocate memory.
- */
-rest_and_return:
- if (!test_thread_flag(TIF_MEMDIE))
- schedule_timeout_uninterruptible(1);
-}
-
/**
* out_of_memory - kill the "best" process when we run out of memory
- * @zonelist: zonelist pointer
+ * @zonelist: zonelist pointer passed to page allocator
* @gfp_mask: memory allocation flags
* @order: amount of memory being requested as a power of 2
* @nodemask: nodemask passed to page allocator
@@ -665,7 +669,7 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
int order, nodemask_t *nodemask)
{
unsigned long freed = 0;
- enum oom_constraint constraint;
+ enum oom_constraint constraint = CONSTRAINT_NONE;
blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
if (freed > 0)
@@ -681,7 +685,8 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
* Check if there were limitations on the allocation (only relevant for
* NUMA) that may require different handling.
*/
- constraint = constrained_alloc(zonelist, gfp_mask, nodemask);
+ if (zonelist)
+ constraint = constrained_alloc(zonelist, gfp_mask, nodemask);
read_lock(&tasklist_lock);
if (unlikely(sysctl_panic_on_oom)) {
/*
@@ -691,6 +696,7 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
*/
if (constraint == CONSTRAINT_NONE) {
dump_header(NULL, gfp_mask, order, NULL);
+ read_unlock(&tasklist_lock);
panic("Out of memory: panic_on_oom is enabled\n");
}
}
@@ -704,3 +710,17 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
if (!test_thread_flag(TIF_MEMDIE))
schedule_timeout_uninterruptible(1);
}
+
+/*
+ * The pagefault handler calls here because it is out of memory, so kill a
+ * memory-hogging task. If a populated zone has ZONE_OOM_LOCKED set, a parallel
+ * oom killing is already in progress so do nothing. If a task is found with
+ * TIF_MEMDIE set, it has been killed so do nothing and allow it to exit.
+ */
+void pagefault_out_of_memory(void)
+{
+ if (!try_set_system_oom())
+ return;
+ out_of_memory(NULL, 0, 0, NULL);
+ clear_system_oom();
+}
--
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