Messages in this thread | | | From | KOSAKI Motohiro <> | Subject | Re: [PATCH 10/11] oom: give the dying task a higher priority | Date | Wed, 30 Jun 2010 18:35:08 +0900 (JST) |
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Sorry, I forgot to cc Luis. resend.
(intentional full quote)
> From: Luis Claudio R. Goncalves <lclaudio@uudg.org> > > 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@uudg.org> > Cc: Minchan Kim <minchan.kim@gmail.com> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> > --- > 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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