Sorry, I forgot to cc Luis. resend.
(intentional full quote)
> From: Luis Claudio R. Goncalves <lclaudio@xxxxxxxx>
>
> In a system under heavy load it was observed that even after the
> oom-killer selects a task to die, the task may take a long time to die.
>
> Right after sending a SIGKILL to the task selected by the oom-killer
> this task has it's priority increased so that it can exit() exit soon,
> freeing memory. That is accomplished by:
>
> /*
> * 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...
> */
> p->rt.time_slice = HZ;
> set_tsk_thread_flag(p, TIF_MEMDIE);
>
> It sounds plausible giving the dying task an even higher priority to be
> sure it will be scheduled sooner and free the desired memory. It was
> suggested on LKML using SCHED_FIFO:1, the lowest RT priority so that
> this task won't interfere with any running RT task.
>
> If the dying task is already an RT task, leave it untouched.
> Another good suggestion, implemented here, was to avoid boosting the
> dying task priority in case of mem_cgroup OOM.
>
> Signed-off-by: Luis Claudio R. Goncalves <lclaudio@xxxxxxxx>
> Cc: Minchan Kim <minchan.kim@xxxxxxxxx>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> ---
> mm/oom_kill.c | 34 +++++++++++++++++++++++++++++++---
> 1 files changed, 31 insertions(+), 3 deletions(-)
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index b5678bf..0858b18 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -82,6 +82,24 @@ 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, ¶m);
> +}
> +
> +/*
> * 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
> * pointer. Return p, or any of its subthreads with a valid ->mm, with
> @@ -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;
> }
>
> --
> 1.6.5.2
>
>
>
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