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

Johannes Weiner
2009-02-02T13:45:35Z

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@linux.vnet.ibm.com>
>
> 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@linux.vnet.ibm.com>
> ---
>
> 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