Re: OOM killer, page fault

[Minchan Kim <minchan.kim@gmail.com>]

On Mon, Nov 2, 2009 at 3:59 PM, KOSAKI Motohiro
<kosaki.motohiro@jp.fujitsu.com> wrote:
>> On Mon,  2 Nov 2009 13:24:06 +0900 (JST)
>> KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:
>>
>> > Hi,
>> >
>> > (Cc to linux-mm)
>> >
>> > Wow, this is very strange log.
>> >
>> > > Dear all,
>> > >
>> > > (please Cc)
>> > >
>> > > With 2.6.32-rc5 I got that one:
>> > > [13832.210068] Xorg invoked oom-killer: gfp_mask=0x0, order=0, oom_adj=0
>> >
>> > order = 0
>>
>> I think this problem results from 'gfp_mask = 0x0'.
>> Is it possible?
>>
>> If it isn't H/W problem, Who passes gfp_mask with 0x0?
>> It's culpit.
>>
>> Could you add BUG_ON(gfp_mask == 0x0) in __alloc_pages_nodemask's head?
>
> No.
> In page fault case, gfp_mask show meaningless value. Please ignore it.
> pagefault_out_of_memory() always pass gfp_mask==0 to oom.
>
>
> mm/oom_kill.c
> ====================================
> void pagefault_out_of_memory(void)
> {
>        unsigned long freed = 0;
>
>        blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
>        if (freed > 0)
>                /* Got some memory back in the last second. */
>                return;
>
>        /*
>         * If this is from memcg, oom-killer is already invoked.
>         * and not worth to go system-wide-oom.
>         */
>        if (mem_cgroup_oom_called(current))
>                goto rest_and_return;
>
>        if (sysctl_panic_on_oom)
>                panic("out of memory from page fault. panic_on_oom is selected.\n");
>
>        read_lock(&tasklist_lock);
>        __out_of_memory(0, 0);       <---- here!
>        read_unlock(&tasklist_lock);
>
>

Yeb. Kame already noticed it. :)
Thanks for pointing me out, again.

I already suggested another patch.
What do you think about it?


-- 
Kind regards,
Minchan Kim

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