Messages in this thread | | | Date | Tue, 3 Feb 2009 10:11:23 +0530 | From | Balbir Singh <> | Subject | Re: [-mm patch] Show memcg information during OOM |
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* David Rientjes <rientjes@google.com> [2009-02-02 13:05:02]:
> On Tue, 3 Feb 2009, Balbir Singh wrote: > > > David, I'd agree, but since we are under printk_ratelimit() and this > > is a not-so-common path, does the log level matter much? If it does, I > > don't mind using KERN_INFO. > > > > It matters for parsing dmesg output; the only KERN_WARNING message from > the oom killer is normally the header. There's a couple extra ones for > error conditions (that could certainly be changed to KERN_ERR), but only > in very rare circumstances. > > As defined by include/linux/kernel.h: > > #define KERN_WARNING "<4>" /* warning conditions */ > ... > #define KERN_INFO "<6>" /* informational */ > > The meminfo you are printing falls under the "informational" category, no? > > While you're there, it might also be helpful to make another change > that would also help in parsing the output: > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 8e4be9c..954b0d5 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -813,6 +813,25 @@ bool mem_cgroup_oom_called(struct task_struct *task) > > rcu_read_unlock(); > > return ret; > > } > > + > > +void mem_cgroup_print_mem_info(struct mem_cgroup *memcg) > > +{ > > + if (!memcg) > > + return; > > + > > + printk(KERN_WARNING "Memory cgroups's name %s\n", > > + memcg->css.cgroup->dentry->d_name.name); > > This should be "cgroup's", but I don't think you want to print this on a > line by itself since the only system-wide synchronization here is a > read-lock on tasklist_lock and there could be two separate memcg's that > are oom. > > So it's quite possible, though unlikely, that two seperate oom events > would have these messages merged together in the ring buffer, which would > make parsing impossible. > > I think you probably want to add the name to each line you print, such as: > > > + printk(KERN_WARNING "Cgroup memory: 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)); > > const char *name = memcg->css.cgroup->dentry->d_name.name; > > printk(KERN_INFO "Cgroup %s memory: usage %llu, limit %llu" > " failcount %llu\n", name, ...); > > > + printk(KERN_WARNING "Cgroup memory+swap: usage %llu, limit %llu " > > + "failcnt %llu\n", > > + res_counter_read_u64(&memcg->memsw, RES_USAGE), > > + res_counter_read_u64(&memcg->memsw, RES_LIMIT), > > + res_counter_read_u64(&memcg->memsw, RES_FAILCNT)); > > and > > printk(KERN_INFO "Cgroup %s memory+swap: usage %llu, limit %llu " > "failcnt %llu\n", name, ...); > > > +} >
Thanks for the review, I'll incorporate as much of it as possible in the next version.
-- Balbir
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