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Date: Thu, 05 Feb 2009 12:00:05 +0800
From: Lai Jiangshan <laijs@...fujitsu.com>
To: balbir@...ux.vnet.ibm.com
CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Andrew Morton <akpm@...ux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
"lizf@...fujitsu.com" <lizf@...fujitsu.com>,
"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [-mm patch] Show memcg information during OOM (v3)
Balbir Singh wrote:
> Description: Add RSS and swap to OOM output from memcg
>
> From: Balbir Singh <balbir@...ux.vnet.ibm.com>
>
> Changelog v3..v2
> 1. Use static char arrays of size PATH_MAX in order to make
> the OOM message more reliable.
>
> Changelog v2..v1:
>
> 1. Add more information about task's memcg and the memcg
> over it's limit
> 2. Print data in KB
> 3. Move the print routine outside task_lock()
> 4. Use rcu_read_lock() around cgroup_path, strictly speaking it
> is not required, but relying on the current memcg implementation
> is not a good idea.
>
>
> This patch displays memcg values like failcnt, usage and limit
> when an OOM occurs due to memcg.
>
> Thanks go out to Johannes Weiner, Li Zefan, David Rientjes,
> Kamezawa Hiroyuki, Daisuke Nishimura and KOSAKI Motohiro for
> review.
>
> Sample output
> -------------
>
> Task in /a/x killed as a result of limit of /a
> memory: usage 1048576kB, limit 1048576kB, failcnt 4183
> memory+swap: usage 1400964kB, limit 9007199254740991kB, failcnt 0
>
> Signed-off-by: Balbir Singh <balbir@...ux.vnet.ibm.com>
> ---
>
> include/linux/memcontrol.h | 6 ++++
> mm/memcontrol.c | 63 ++++++++++++++++++++++++++++++++++++++++++++
> mm/oom_kill.c | 1 +
> 3 files changed, 70 insertions(+), 0 deletions(-)
>
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 326f45c..f9a6e78 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -104,6 +104,8 @@ 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_oom_info(struct mem_cgroup *memcg,
> + struct task_struct *p);
>
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> extern int do_swap_account;
> @@ -270,6 +272,10 @@ mem_cgroup_get_reclaim_stat_from_page(struct page *page)
> return NULL;
> }
>
> +void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
> +{
> +}
> +
> #endif /* CONFIG_CGROUP_MEM_CONT */
>
> #endif /* _LINUX_MEMCONTROL_H */
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 8e4be9c..44e053b 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -27,6 +27,7 @@
> #include <linux/backing-dev.h>
> #include <linux/bit_spinlock.h>
> #include <linux/rcupdate.h>
> +#include <linux/limits.h>
> #include <linux/mutex.h>
> #include <linux/slab.h>
> #include <linux/swap.h>
> @@ -813,6 +814,68 @@ bool mem_cgroup_oom_called(struct task_struct *task)
> rcu_read_unlock();
> return ret;
> }
> +
> +/**
> + * mem_cgroup_print_mem_info: Called from OOM with tasklist_lock held in
> + * read mode.
> + * @memcg: The memory cgroup that went over limit
> + * @p: Task that is going to be killed
> + *
> + * NOTE: @memcg and @p's mem_cgroup can be different when hierarchy is
> + * enabled
> + */
> +void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
> +{
> + struct cgroup *task_cgrp;
> + struct cgroup *mem_cgrp;
> + /*
> + * Need a buffer on stack, can't rely on allocations. The code relies
> + * on the assumption that OOM is serialized for memory controller.
> + * If this assumption is broken, revisit this code.
> + */
> + static char task_memcg_name[PATH_MAX];
> + static char memcg_name[PATH_MAX];
Is there any lock which protects this static data?
> + int ret;
> +
> + if (!memcg)
> + return;
> +
> + mem_cgrp = memcg->css.cgroup;
> + task_cgrp = mem_cgroup_from_task(p)->css.cgroup;
> +
> + rcu_read_lock();
> + ret = cgroup_path(task_cgrp, task_memcg_name, PATH_MAX);
> + if (ret < 0) {
> + /*
> + * Unfortunately, we are unable to convert to a useful name
> + * But we'll still print out the usage information
> + */
> + rcu_read_unlock();
> + goto done;
> + }
> + ret = cgroup_path(mem_cgrp, memcg_name, PATH_MAX);
> + if (ret < 0) {
> + rcu_read_unlock();
> + goto done;
> + }
> +
> + rcu_read_unlock();
IIRC, a preempt_enable() will add about 50 bytes to kernel size.
I think these lines are also good for readability:
rcu_read_lock();
ret = cgroup_path(task_cgrp, task_memcg_name, PATH_MAX);
if (ret >= 0)
ret = cgroup_path(mem_cgrp, memcg_name, PATH_MAX);
rcu_read_unlock();
if (ret < 0) {
/*
* Unfortunately, we are unable to convert to a useful name
* But we'll still print out the usage information
*/
goto done;
}
Lai
> +
> + printk(KERN_INFO "Task in %s killed as a result of limit of %s\n",
> + task_memcg_name, memcg_name);
> +done:
> +
> + printk(KERN_INFO "memory: usage %llukB, limit %llukB, failcnt %llu\n",
> + res_counter_read_u64(&memcg->res, RES_USAGE) >> 10,
> + res_counter_read_u64(&memcg->res, RES_LIMIT) >> 10,
> + res_counter_read_u64(&memcg->res, RES_FAILCNT));
> + printk(KERN_INFO "memory+swap: usage %llukB, limit %llukB, "
> + "failcnt %llu\n",
> + res_counter_read_u64(&memcg->memsw, RES_USAGE) >> 10,
> + res_counter_read_u64(&memcg->memsw, RES_LIMIT) >> 10,
> + res_counter_read_u64(&memcg->memsw, 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..2f3166e 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -394,6 +394,7 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
> cpuset_print_task_mems_allowed(current);
> task_unlock(current);
> dump_stack();
> + mem_cgroup_print_oom_info(mem, current);
> show_mem();
> if (sysctl_oom_dump_tasks)
> dump_tasks(mem);
>
--
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