oom: give the dying task a higher priority

[firefly-linux-kernel-4.4.55.git] / mm / oom_kill.c

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 942861bf91774fc7f706ee8d19cd8f150a18e987..31bd0c344fa771cb31a5479cbde4d7983678f614 100644 (file)
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -81,6 +81,24 @@ static bool has_intersects_mems_allowed(struct task_struct *tsk,
 }
 #endif /* CONFIG_NUMA */
 
+/*
+ * If this is a system OOM (not a memcg OOM) and the task selected to be
+ * killed is not already running at high (RT) priorities, speed up the
+ * recovery by boosting the dying task to the lowest FIFO priority.
+ * That helps with the recovery and avoids interfering with RT tasks.
+ */
+static void boost_dying_task_prio(struct task_struct *p,
+                                 struct mem_cgroup *mem)
+{
+       struct sched_param param = { .sched_priority = 1 };
+
+       if (mem)
+               return;
+
+       if (!rt_task(p))
+               sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
+}
+
 /*
  * The process p may have detached its own ->mm while exiting or through
  * use_mm(), but one or more of its subthreads may still have a valid
@@ -421,7 +439,7 @@ static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
 }
 
 #define K(x) ((x) << (PAGE_SHIFT-10))
-static int oom_kill_task(struct task_struct *p)
+static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem)
 {
        p = find_lock_task_mm(p);
        if (!p) {
@@ -434,9 +452,17 @@ static int oom_kill_task(struct task_struct *p)
                K(get_mm_counter(p->mm, MM_FILEPAGES)));
        task_unlock(p);
 
-       p->rt.time_slice = HZ;
+
        set_tsk_thread_flag(p, TIF_MEMDIE);
        force_sig(SIGKILL, p);
+
+       /*
+        * We give our sacrificial lamb high priority and access to
+        * all the memory it needs. That way it should be able to
+        * exit() and clear out its resources quickly...
+        */
+       boost_dying_task_prio(p, mem);
+
        return 0;
 }
 #undef K
@@ -460,6 +486,7 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
         */
        if (p->flags & PF_EXITING) {
                set_tsk_thread_flag(p, TIF_MEMDIE);
+               boost_dying_task_prio(p, mem);
                return 0;
        }
 
@@ -489,7 +516,7 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
                }
        } while_each_thread(p, t);
 
-       return oom_kill_task(victim);
+       return oom_kill_task(victim, mem);
 }
 
 /*
@@ -670,6 +697,7 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
         */
        if (fatal_signal_pending(current)) {
                set_thread_flag(TIF_MEMDIE);
+               boost_dying_task_prio(current, NULL);
                return;
        }