linux-kernel - Re: [PATCH v2] Print the memcg's name when system-wide OOM happened

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Message-ID: <20180518062213.GA21711@dhcp22.suse.cz>
Date:   Fri, 18 May 2018 08:22:13 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     ufo19890607 <ufo19890607@...il.com>
Cc:     akpm@...ux-foundation.org, rientjes@...gle.com,
        kirill.shutemov@...ux.intel.com, aarcange@...hat.com,
        penguin-kernel@...ove.SAKURA.ne.jp, guro@...com,
        yang.s@...baba-inc.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        yuzhoujian <yuzhoujian@...ichuxing.com>
Subject: Re: [PATCH v2] Print the memcg's name when system-wide OOM happened

On Fri 18-05-18 04:07:14, ufo19890607 wrote:
> From: yuzhoujian <yuzhoujian@...ichuxing.com>
> 
> The dump_header does not print the memcg's name when the system
> oom happened. So users cannot locate the certain container which
> contains the task that has been killed by the oom killer. System
> oom report will contain the memcg's name after this patch.

It would be great to mention what you can the name for.

> Changes since v1:
> - replace adding mem_cgroup_print_oom_info with printing the memcg's
>   name only.
> 
> Signed-off-by: yuzhoujian <yuzhoujian@...ichuxing.com>
> ---
>  mm/oom_kill.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 8ba6cb88cf58..b0abb5930232 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -433,6 +433,9 @@ static void dump_header(struct oom_control *oc, struct task_struct *p)
>  	if (is_memcg_oom(oc))
>  		mem_cgroup_print_oom_info(oc->memcg, p);
>  	else {
> +		pr_info("Task in ");
> +		pr_cont_cgroup_path(task_cgroup(p, memory_cgrp_id));
> +		pr_cont(" killed as a result of limit of ");
>  		show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask);
>  		if (is_dump_unreclaim_slabs())
>  			dump_unreclaimable_slab();

I bet this doesn't compile with CONFIG_MEMCG=n. You either need to put
these pr_info lines inside ifdef CONFIG_MEMCG or add helper. The later
would reduce code duplication.
-- 
Michal Hocko
SUSE Labs