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

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Date:	Tue, 10 May 2011 16:29:02 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.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

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.

> 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.

>          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.

I think the cpu should also be removed.

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

> 
> 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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