On Fri 09-11-12 18:23:07, Sha Zhengju wrote:
> On 11/09/2012 12:25 AM, Michal Hocko wrote:
> >On Thu 08-11-12 23:52:47, Sha Zhengju wrote:
[...]
> >>+ for (i = 0; i< MEM_CGROUP_STAT_NSTATS; i++) {
> >>+ long long val = 0;
> >>+ if (i == MEM_CGROUP_STAT_SWAP&& !do_swap_account)
> >>+ continue;
> >>+ for_each_mem_cgroup_tree(mi, memcg)
> >>+ val += mem_cgroup_read_stat(mi, i);
> >>+ printk(KERN_CONT "%s:%lldKB ", mem_cgroup_stat_names[i],
> >>K(val));
> >>+ }
> >>+
> >>+ for (i = 0; i< NR_LRU_LISTS; i++) {
> >>+ unsigned long long val = 0;
> >>+
> >>+ for_each_mem_cgroup_tree(mi, memcg)
> >>+ val += mem_cgroup_nr_lru_pages(mi, BIT(i));
> >>+ printk(KERN_CONT "%s:%lluKB ", mem_cgroup_lru_names[i], K(val));
> >>+ }
> >>+ printk(KERN_CONT "\n");
> >This is nice and simple I am just thinking whether it is enough. Say
> >that you have a deeper hierarchy and the there is a safety limit in the
> >its root
> > A (limit)
> > /|\
> > B C D
> > |\
> > E F
> >
> >and we trigger an OOM on the A's limit. Now we know that something blew
> >up but what it was we do not know. Wouldn't it be better to swap the for
> >and for_each_mem_cgroup_tree loops? Then we would see the whole
> >hierarchy and can potentially point at the group which doesn't behave.
> >Memory cgroup stats for A/: ...
> >Memory cgroup stats for A/B/: ...
> >Memory cgroup stats for A/C/: ...
> >Memory cgroup stats for A/D/: ...
> >Memory cgroup stats for A/D/E/: ...
> >Memory cgroup stats for A/D/F/: ...
> >
> >Would it still fit in with your use case?
> >[...]
>
> We haven't used those complicate hierarchy yet, but it sounds a good
> suggestion. :)
> Hierarchy is a little complex to use from our experience, and the
> three cgroups involved in memcg oom can be different: memcg of
> invoker, killed task, memcg of going over limit.Suppose a process in
> B triggers oom and a victim in root A is selected to be killed, we
> may as well want to know memcg stats just local in A cgroup(excludes
> BCD). So besides hierarchy info, does it acceptable to also print
> the local root node stats which as I did in the V1
> version(https://lkml.org/lkml/2012/7/30/179).
Ohh, I probably wasn't clear enough. I didn't suggest cumulative
numbers. Only per group. So it would be something like:
for_each_mem_cgroup_tree(mi, memcg) {
printk("Memory cgroup stats for %s", memcg_name);
for (i = 0; i< MEM_CGROUP_STAT_NSTATS; i++) {
if (i == MEM_CGROUP_STAT_SWAP&& !do_swap_account)
continue;
printk(KERN_CONT "%s:%lldKB ", mem_cgroup_stat_names[i],
K(mem_cgroup_read_stat(mi, i)));
}
for (i = 0; i< NR_LRU_LISTS; i++)
printk(KERN_CONT "%s:%lluKB ", mem_cgroup_lru_names[i],
K(mem_cgroup_nr_lru_pages(mi, BIT(i))));
printk(KERN_CONT"\n");
}
> Another one I'm hesitating is numa stats, it seems the output is
> beginning to get more and more....
NUMA stats are basically per node - per zone LRU data and that the
for(NR_LRU_LISTS) can be easily extended to cover that.
--
Michal Hocko
SUSE Labs
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