Messages in this thread | | | Date | Thu, 1 Apr 2010 01:35:02 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [patch] oom: give current access to memory reserves if it has been killed |
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On Wed, 31 Mar 2010, Oleg Nesterov wrote:
> Probably something like the patch below makes sense. Note that > "skip kernel threads" logic is wrong too, we should check PF_KTHREAD. > Probably it is better to check it in select_bad_process() instead, > near is_global_init(). >
is_global_init() will be true for p->flags & PF_KTHREAD.
> The new helper, find_lock_task_mm(), should be used by > oom_forkbomb_penalty() too. > > dump_tasks() doesn't need it, it does do_each_thread(). Cough, > __out_of_memory() and out_of_memory() call it without tasklist. > We are going to panic() anyway, but still. >
Indeed, good observation.
> Oleg. > > --- x/mm/oom_kill.c > +++ x/mm/oom_kill.c > @@ -129,6 +129,19 @@ static unsigned long oom_forkbomb_penalt > (child_rss / sysctl_oom_forkbomb_thres) : 0; > } > > +static find_lock_task_mm(struct task_struct *p) > +{ > + struct task_struct *t = p; > + do { > + task_lock(t); > + if (likely(t->mm && !(t->flags & PF_KTHREAD))) > + return t; > + task_unlock(t); > + } while_each_thred(p, t); > + > + return NULL; > +} > + > /** > * oom_badness - heuristic function to determine which candidate task to kill > * @p: task struct of which task we should calculate > @@ -159,13 +172,9 @@ unsigned int oom_badness(struct task_str > if (p->flags & PF_OOM_ORIGIN) > return 1000; > > - task_lock(p); > - mm = p->mm; > - if (!mm) { > - task_unlock(p); > + p = find_lock_task_mm(p); > + if (!p) > return 0; > - } > - > /* > * The baseline for the badness score is the proportion of RAM that each > * task's rss and swap space use. > @@ -330,12 +339,6 @@ static struct task_struct *select_bad_pr > *ppoints = 1000; > } > > - /* > - * skip kernel threads and tasks which have already released > - * their mm. > - */ > - if (!p->mm) > - continue; > if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) > continue;
You can't do this for the reason I cited in another email, oom_badness() returning 0 does not exclude a task from being chosen by selcet_bad_process(), it will use that task if nothing else has been found yet. We must explicitly filter it from consideration by checking for !p->mm.
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