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Date: Mon, 23 May 2011 12:59:35 +0900 From: Minchan Kim <minchan.kim@...il.com> To: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, akpm@...ux-foundation.org, caiqian@...hat.com, rientjes@...gle.com, hughd@...gle.com, kamezawa.hiroyu@...fujitsu.com, oleg@...hat.com Subject: Re: [PATCH 3/5] oom: oom-killer don't use proportion of system-ram internally 2011/5/20 KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>: > CAI Qian reported his kernel did hang-up if he ran fork intensive > workload and then invoke oom-killer. > > The problem is, current oom calculation uses 0-1000 normalized value > (The unit is a permillage of system-ram). Its low precision make > a lot of same oom score. IOW, in his case, all processes have smaller > oom score than 1 and internal calculation round it to 1. > > Thus oom-killer kill ineligible process. This regression is caused by > commit a63d83f427 (oom: badness heuristic rewrite). > > The solution is, the internal calculation just use number of pages > instead of permillage of system-ram. And convert it to permillage > value at displaying time. > > This patch doesn't change any ABI (included /proc/<pid>/oom_score_adj) > even though current logic has a lot of my dislike thing. > > Reported-by: CAI Qian <caiqian@...hat.com> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> > --- > fs/proc/base.c | 13 ++++++---- > include/linux/oom.h | 7 +---- > mm/oom_kill.c | 60 +++++++++++++++++++++++++++++++++----------------- > 3 files changed, 49 insertions(+), 31 deletions(-) > > diff --git a/fs/proc/base.c b/fs/proc/base.c > index dfa5327..d6b0424 100644 > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -476,14 +476,17 @@ static const struct file_operations proc_lstats_operations = { > > static int proc_oom_score(struct task_struct *task, char *buffer) > { > - unsigned long points = 0; > + unsigned long points; > + unsigned long ratio = 0; > + unsigned long totalpages = totalram_pages + total_swap_pages + 1; Does we need +1? oom_badness does have the check. > > read_lock(&tasklist_lock); > - if (pid_alive(task)) > - points = oom_badness(task, NULL, NULL, > - totalram_pages + total_swap_pages); > + if (pid_alive(task)) { > + points = oom_badness(task, NULL, NULL, totalpages); > + ratio = points * 1000 / totalpages; > + } > read_unlock(&tasklist_lock); > - return sprintf(buffer, "%lu\n", points); > + return sprintf(buffer, "%lu\n", ratio); > } > > struct limit_names { > diff --git a/include/linux/oom.h b/include/linux/oom.h > index 5e3aa83..0f5b588 100644 > --- a/include/linux/oom.h > +++ b/include/linux/oom.h > @@ -40,7 +40,8 @@ enum oom_constraint { > CONSTRAINT_MEMCG, > }; > > -extern unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem, > +/* The badness from the OOM killer */ > +extern unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *mem, > const nodemask_t *nodemask, unsigned long totalpages); > extern int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_flags); > extern void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_flags); > @@ -62,10 +63,6 @@ static inline void oom_killer_enable(void) > oom_killer_disabled = false; > } > > -/* The badness from the OOM killer */ > -extern unsigned long badness(struct task_struct *p, struct mem_cgroup *mem, > - const nodemask_t *nodemask, unsigned long uptime); > - > extern struct task_struct *find_lock_task_mm(struct task_struct *p); > > /* sysctls */ > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index e6a6c6f..8bbc3df 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -132,10 +132,12 @@ static bool oom_unkillable_task(struct task_struct *p, > * predictable as possible. The goal is to return the highest value for the > * task consuming the most memory to avoid subsequent oom failures. > */ > -unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem, > +unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *mem, > const nodemask_t *nodemask, unsigned long totalpages) > { > - int points; > + unsigned long points; > + unsigned long score_adj = 0; > + > > if (oom_unkillable_task(p, mem, nodemask)) > return 0; > @@ -160,7 +162,7 @@ unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem, > */ > if (p->flags & PF_OOM_ORIGIN) { > task_unlock(p); > - return 1000; > + return ULONG_MAX; > } > > /* > @@ -176,33 +178,49 @@ unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem, > */ > points = get_mm_rss(p->mm) + p->mm->nr_ptes; > points += get_mm_counter(p->mm, MM_SWAPENTS); > - > - points *= 1000; > - points /= totalpages; > task_unlock(p); > > /* > * Root processes get 3% bonus, just like the __vm_enough_memory() > * implementation used by LSMs. > + * > + * XXX: Too large bonus, example, if the system have tera-bytes memory.. > */ > - if (has_capability_noaudit(p, CAP_SYS_ADMIN)) > - points -= 30; > + if (has_capability_noaudit(p, CAP_SYS_ADMIN)) { > + if (points >= totalpages / 32) > + points -= totalpages / 32; > + else > + points = 0; Odd. Why do we initialize points with 0? I think the idea is good. -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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