linux-kernel - Re: [PATCH 1/4] oom: improve dump

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Message-ID: <4DCD049B.4050003@jp.fujitsu.com>
Date:	Fri, 13 May 2011 19:14:51 +0900
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	David Rientjes <rientjes@...gle.com>
CC:	CAI Qian <caiqian@...hat.com>, avagin@...il.com,
	Andrey Vagin <avagin@...nvz.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Minchan Kim <minchan.kim@...il.com>,
	Hugh Dickins <hughd@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH 1/4] oom: improve dump_tasks() show items

Hi

Sorry for the delay. I did hit machine crash in this week and I lost
a lot of e-mail.


> On Tue, 10 May 2011, KOSAKI Motohiro wrote:
>
>> Recently, oom internal logic was dramatically changed. Thus
>> dump_tasks() is no longer useful. it has some meaningless
>> items and don't have some oom socre related items.
>>
>
> This changelog is inaccurate.
>
> dump_tasks() is actually useful as it currently stands; there are things
> that you may add or remove but saying that it is "no longer useful" is an
> exaggeration.

Hm. OK.

>
>> This patch adapt displaying fields to new oom logic.
>>
>> details
>> ==========
>> removed: pid (we always kill process. don't need thread id),
>>           mm->total_vm (we no longer uses virtual memory size)
>
> Showing mm->total_vm is still interesting to know what the old heuristic
> would have used rather than the new heuristic, I'd prefer if we kept it.

OK, reasonable.



>
>>           signal->oom_adj (we no longer uses it internally)
>> added: ppid (we often kill sacrifice child process)
>> modify: RSS (account mm->nr_ptes too)
>
> I'd prefer if ptes were shown independently from rss instead of adding it
> to the thread's true rss usage and representing it as such.

No. nr-pte should always be accounted as rss. I plan to change RLIMIT_RSS too.
Because, when end users change RLIMIT_RSS, they intend to limit number of physical
memory usage. It's not only subset. current total_rss = anon-rss + file-rss is
only implementation limit. In the other hand, if we makes separate RLIMIT, RLIMIT_RSS
and RLIMIT_PTE, RLIMIT_RSS don't prevent zero page DoS attack. it's no optimal.


> I think the cpu should also be removed.

ok.


> For the next version, could you show the old output and comparsion to new
> output in the changelog?

Will do.


>
>>
>> Signed-off-by: KOSAKI Motohiro<kosaki.motohiro@...fujitsu.com>
>> ---
>>
>> Strictly speaking. this is NOT a part of oom fixing patches. but it's
>> necessary when I parse QAI's test result.
>>
>>
>>   mm/oom_kill.c |   14 ++++++++------
>>   1 files changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
>> index f52e85c..118d958 100644
>> --- a/mm/oom_kill.c
>> +++ b/mm/oom_kill.c
>> @@ -355,7 +355,7 @@ static void dump_tasks(const struct mem_cgroup *mem, const nodemask_t *nodemask)
>>   	struct task_struct *p;
>>   	struct task_struct *task;
>>
>> -	pr_info("[ pid ]   uid  tgid total_vm      rss cpu oom_adj oom_score_adj name\n");
>> +	pr_info("[   pid]   ppid   uid      rss  cpu score_adj name\n");
>>   	for_each_process(p) {
>>   		if (oom_unkillable_task(p, mem, nodemask))
>>   			continue;
>> @@ -370,11 +370,13 @@ static void dump_tasks(const struct mem_cgroup *mem, const nodemask_t *nodemask)
>>   			continue;
>>   		}
>>
>> -		pr_info("[%5d] %5d %5d %8lu %8lu %3u     %3d         %5d %s\n",
>> -			task->pid, task_uid(task), task->tgid,
>> -			task->mm->total_vm, get_mm_rss(task->mm),
>> -			task_cpu(task), task->signal->oom_adj,
>> -			task->signal->oom_score_adj, task->comm);
>> +		pr_info("[%6d] %6d %5d %8lu %4u %9d %s\n",
>> +			task_tgid_nr(task), task_tgid_nr(task->real_parent),
>> +			task_uid(task),
>> +			get_mm_rss(task->mm) + p->mm->nr_ptes,
>> +			task_cpu(task),
>> +			task->signal->oom_score_adj,
>> +			task->comm);
>>   		task_unlock(task);
>>   	}
>>   }
>
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>


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