Messages in this thread |  | | | Date | Thu, 05 Feb 2009 12:00:05 +0800 | | From | Lai Jiangshan <> | | Subject | Re: [-mm patch] Show memcg information during OOM (v3) |
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Balbir Singh wrote: > Description: Add RSS and swap to OOM output from memcg > > From: Balbir Singh <balbir@linux.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@linux.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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