linux-kernel - Re: [PATCH for -mm] getrusage: fill ru

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Date:	Sun, 4 Jan 2009 06:13:16 +0900
From:	"KOSAKI Motohiro" <kosaki.motohiro@...fujitsu.com>
To:	"Oleg Nesterov" <oleg@...hat.com>
Cc:	"Jiri Pirko" <jpirko@...hat.com>, linux-kernel@...r.kernel.org,
	"Hugh Dickins" <hugh@...itas.com>, linux-mm <linux-mm@...ck.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: [PATCH for -mm] getrusage: fill ru_maxrss value

> sorry for delay!
>
>>
>> Jiri's resend3 -> v1
>>  - At wait_task_zombie(), parent process doesn't only collect child maxrss,
>>    but also cmaxrss.
>
> Ah yes, this looks very right to me.

hehe, therefore I like testcase driven development :)


>>  - ru_maxrss inherit at exec()
>
> I must admit, I hate this ;)

Your feelings are understood well.


> That said, I agree with you point about compatibility. So I have to
> agree with this change.
>
> Still, I'd like to know what other people think ;)

Yeah, me too.


> And I also agree that xacct is linux specific feature, but I still
> I dislike the fact that xacct and getrusage report different numbers.
> Perhaps we should change xacct as well?

I don't have any strong opinion.
it seems good idea. but I don't know xacct so much.



>
>> --- a/kernel/exit.c   2008-12-29 23:27:59.000000000 +0900
>> +++ b/kernel/exit.c   2008-12-31 21:08:08.000000000 +0900
>> @@ -1053,6 +1053,12 @@ NORET_TYPE void do_exit(long code)
>>       if (group_dead) {
>>               hrtimer_cancel(&tsk->signal->real_timer);
>>               exit_itimers(tsk->signal);
>> +             if (tsk->mm) {
>> +                     unsigned long hiwater_rss = get_mm_hiwater_rss(tsk->mm);
>> +
>> +                     if (tsk->signal->maxrss < hiwater_rss)
>> +                             tsk->signal->maxrss = hiwater_rss;
>> +             }
> [...snip...]
>> --- a/fs/exec.c       2008-12-25 08:26:37.000000000 +0900
>> +++ b/fs/exec.c       2008-12-31 21:11:28.000000000 +0900
>> @@ -870,6 +870,13 @@ static int de_thread(struct task_struct
>>       sig->notify_count = 0;
>>
>>  no_thread_group:
>> +     if (current->mm) {
>> +             unsigned long hiwater_rss = get_mm_hiwater_rss(current->mm);
>> +
>> +             if (sig->maxrss < hiwater_rss)
>> +                     sig->maxrss = hiwater_rss;
>> +     }
>
> Perhaps it makes sense to factor out this code and make a helper?
>
> Unfortunately, exit_mm() and exec_mmap() do not have the common
> path which can update sig->maxrss, mm_release() can't do this...

last problem are, function name and which file have it :)


>> +     if (who != RUSAGE_CHILDREN) {
>> +             struct mm_struct *mm = get_task_mm(p);
>> +             if (mm) {
>> +                     unsigned long hiwater_rss = get_mm_hiwater_rss(mm);
>> +
>> +                     if (maxrss < hiwater_rss)
>> +                             maxrss = hiwater_rss;
>> +                     mmput(mm);
>> +             }
>> +     }
>> +     r->ru_maxrss = maxrss * (PAGE_SIZE / 1024); /* convert pages to KBs */
>
> Hmm... So, RUSAGE_THREAD always report maxrss == get_mm_hiwater_rss(mm)
> and ignores signal->maxrss. Doesn't look right to me...
>
> Unless I missed something, Jiris's patch was fine, but given that now
> we inherit maxrss at exec(), signal->maxrss can have the "inherited"
> value?

you are right. thanks.
will fix.
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