mm: oom-kill: Add lmk_kill possible for ULMK

While ULMK is active, prevent OOM for order <= COSTLY_ORDER
pages. No special actions are taken for larger orders.

Change-Id: I4ccba1b71155947569acc3d88ae2027e3b2e0620
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>

include/linux/oom.h

@@ -115,6 +115,18 @@ extern struct task_struct *find_lock_task_mm(struct task_struct *p);
 
 extern void dump_tasks(struct mem_cgroup *memcg,
 		       const nodemask_t *nodemask);
+
+#ifdef CONFIG_HAVE_USERSPACE_LOW_MEMORY_KILLER
+extern bool should_ulmk_retry(void);
+extern void ulmk_update_last_kill(void);
+#else
+static inline bool should_ulmk_retry(void)
+{
+	return false;
+}
+static inline void ulmk_update_last_kill(void) {}
+#endif
+
 /* sysctls */
 extern int sysctl_oom_dump_tasks;
 extern int sysctl_oom_kill_allocating_task;

kernel/signal.c

@@ -1370,8 +1370,10 @@ int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p,
 
 	if (!ret && sig) {
 		ret = do_send_sig_info(sig, info, p, type);
-		if (capable(CAP_KILL) && sig == SIGKILL)
+		if (capable(CAP_KILL) && sig == SIGKILL) {
 			add_to_oom_reaper(p);
+			ulmk_update_last_kill();
+		}
 	}
 
 	return ret;

mm/Kconfig

@@ -803,6 +803,15 @@ config SPECULATIVE_PAGE_FAULT
 	 allocating, it is failing its processing and a classic page fault
 	 is then tried.
 
+config HAVE_USERSPACE_LOW_MEMORY_KILLER
+	bool "Have userspace low memory killer"
+	default n
+	help
+	  The page allocator cannot directly call into a
+	  userspace low memory killer as it can call into the OOM killer.
+	  Therefore, add a timeout mechanism to give the userspace
+	  low memory killer a chance to run.
+
 config GUP_BENCHMARK
 	bool "Enable infrastructure for get_user_pages_fast() benchmarking"
 	default n

mm/oom_kill.c

@@ -66,6 +66,28 @@ int sysctl_reap_mem_on_sigkill;
  */
 DEFINE_MUTEX(oom_lock);
 
+/*
+ * If ULMK has killed a process recently,
+ * we are making progress.
+ */
+
+#ifdef CONFIG_HAVE_USERSPACE_LOW_MEMORY_KILLER
+static atomic64_t ulmk_kill_jiffies = ATOMIC64_INIT(INITIAL_JIFFIES);
+
+
+bool should_ulmk_retry(void)
+{
+	unsigned long j = atomic64_read(&ulmk_kill_jiffies);
+
+	return time_before(jiffies, j + 2 * HZ);
+}
+
+void ulmk_update_last_kill(void)
+{
+	atomic64_set(&ulmk_kill_jiffies, jiffies);
+}
+#endif
+
 #ifdef CONFIG_NUMA
 /**
  * has_intersects_mems_allowed() - check task eligiblity for kill

mm/page_alloc.c

@@ -4365,6 +4365,9 @@ retry:
 	if (costly_order && !(gfp_mask & __GFP_RETRY_MAYFAIL))
 		goto nopage;
 
+	if (order <= PAGE_ALLOC_COSTLY_ORDER && should_ulmk_retry())
+		goto retry;
+
 	if (should_reclaim_retry(gfp_mask, order, ac, alloc_flags,
 				 did_some_progress > 0, &no_progress_loops))
 		goto retry;