Re: [-mm patch] Show memcg information during OOM

[Johannes Weiner]

On Mon, Feb 02, 2009 at 06:22:40PM +0530, Balbir Singh wrote:
> Hi, All,
> 
> I found the following patch useful while debugging the memory
> controller. It adds additional information if memcg invoked the OOM.
> 
> Comments, Suggestions?
> 
> From: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
> 
> Description: Add RSS and swap to OOM output from memcg
> 
> This patch displays memcg values like failcnt, usage and limit
> when an OOM occurs due to memcg.
> 
> Signed-off-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
> ---
> 
>  include/linux/memcontrol.h |    5 +++++
>  mm/memcontrol.c            |   15 +++++++++++++++
>  mm/oom_kill.c              |    1 +
>  3 files changed, 21 insertions(+), 0 deletions(-)
> 
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 326f45c..2ce1737 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -104,6 +104,7 @@ struct zone_reclaim_stat *mem_cgroup_get_reclaim_stat(struct mem_cgroup *memcg,
>  						      struct zone *zone);
>  struct zone_reclaim_stat*
>  mem_cgroup_get_reclaim_stat_from_page(struct page *page);
> +extern void mem_cgroup_print_mem_info(struct mem_cgroup *memcg);
>  
>  #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
>  extern int do_swap_account;
> @@ -270,6 +271,10 @@ mem_cgroup_get_reclaim_stat_from_page(struct page *page)
>  	return NULL;
>  }
>  
> +void mem_cgroup_print_mem_info(struct mem_cgroup *memcg)
> +{
> +}
> +
>  #endif /* CONFIG_CGROUP_MEM_CONT */
>  
>  #endif /* _LINUX_MEMCONTROL_H */
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 8e4be9c..75eae85 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -813,6 +813,21 @@ bool mem_cgroup_oom_called(struct task_struct *task)
>  	rcu_read_unlock();
>  	return ret;
>  }
> +
> +void mem_cgroup_print_mem_info(struct mem_cgroup *memcg)
> +{
> +	printk(KERN_WARNING "Memory cgroups's name %s\n",
> +		memcg->css.cgroup->dentry->d_name.name);
> +	printk(KERN_WARNING "Memory cgroup RSS : usage %llu, limit %llu"
> +		" failcnt %llu\n", res_counter_read_u64(&memcg->res, RES_USAGE),
> +		res_counter_read_u64(&memcg->res, RES_LIMIT),
> +		res_counter_read_u64(&memcg->res, RES_FAILCNT));
> +	printk(KERN_WARNING "Memory cgroup swap: usage %llu, limit %llu "
> +		"failcnt %llu\n", res_counter_read_u64(&memcg->res, RES_USAGE),
> +		res_counter_read_u64(&memcg->res, RES_LIMIT),
> +		res_counter_read_u64(&memcg->res, RES_FAILCNT));
> +}
> +
>  /*
>   * Unlike exported interface, "oom" parameter is added. if oom==true,
>   * oom-killer can be invoked.
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index d3b9bac..b8e53ae 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -392,6 +392,7 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
>  			current->comm, gfp_mask, order, current->oomkilladj);
>  		task_lock(current);
>  		cpuset_print_task_mems_allowed(current);
> +		mem_cgroup_print_mem_info(mem);

mem is only !NULL when we come from mem_cgroup_out_of_memory().  This
crashes otherwise in mem_cgroup_print_mem_info(), no?

	Hannes
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