On Wed, Mar 13, 2013 at 9:12 AM, Kamezawa Hiroyuki
<kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> (2013/03/12 19:09), Sha Zhengju wrote:
>> If memcg is enabled and no non-root memcg exists, all allocated pages
>> belong to root_mem_cgroup and go through root memcg statistics routines
>> which brings some overheads.
>>
>> So for the sake of performance, we can give up accounting stats of root
>> memcg for MEM_CGROUP_STAT_CACHE/RSS and instead we pay special attention
>> to memcg_stat_show() while showing root memcg numbers:
>> as we don't account root memcg stats anymore, the root_mem_cgroup->stat
>> numbers are actually 0. So we fake these numbers by using stats of global
>> state and all other memcg. That is for root memcg:
>>
>> nr(MEM_CGROUP_STAT_CACHE) = global_page_state(NR_FILE_PAGES) -
>> sum_of_all_memcg(MEM_CGROUP_STAT_CACHE);
>>
>> Rss pages accounting are in the similar way.
>>
>> Signed-off-by: Sha Zhengju <handai.szj@xxxxxxxxxx>
>> ---
>> mm/memcontrol.c | 50 ++++++++++++++++++++++++++++++++++----------------
>> 1 file changed, 34 insertions(+), 16 deletions(-)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 735cd41..e89204f 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -958,26 +958,27 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
>> {
>> preempt_disable();
>>
>> - /*
>> - * Here, RSS means 'mapped anon' and anon's SwapCache. Shmem/tmpfs is
>> - * counted as CACHE even if it's on ANON LRU.
>> - */
>> - if (anon)
>> - __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_RSS],
>> - nr_pages);
>> - else
>> - __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_CACHE],
>> - nr_pages);
>> -
>> /* pagein of a big page is an event. So, ignore page size */
>> if (nr_pages > 0)
>> __this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PGPGIN]);
>> - else {
>> + else
>> __this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PGPGOUT]);
>> - nr_pages = -nr_pages; /* for event */
>> - }
>>
>> - __this_cpu_add(memcg->stat->nr_page_events, nr_pages);
>> + __this_cpu_add(memcg->stat->nr_page_events,
>> + nr_pages < 0 ? -nr_pages : nr_pages);
>> +
>> + if (!mem_cgroup_is_root(memcg)) {
>> + /*
>> + * Here, RSS means 'mapped anon' and anon's SwapCache. Shmem/tmpfs is
>> + * counted as CACHE even if it's on ANON LRU.
>> + */
>> + if (anon)
>> + __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_RSS],
>> + nr_pages);
>> + else
>> + __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_CACHE],
>> + nr_pages);
>> + }
>
> Hmm. I don't like to add this check to this fast path. IIUC, with Costa's patch, root memcg
> will not make any charges at all and never call this function. I like his one rather than
Yes. But I think that one still has some other problems such as
PGPGIN/PGPGOUT and threshold events related things. I prefer to
improve this as a start.
Thanks,
Sha
> this patching.
>
> Thanks,
> -Kame
>
>
>>
>> preempt_enable();
>> }
>> @@ -5445,12 +5446,24 @@ static int memcg_stat_show(struct cgroup *cont, struct cftype *cft,
>> struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
>> struct mem_cgroup *mi;
>> unsigned int i;
>> + enum zone_stat_item global_stat[] = {NR_FILE_PAGES, NR_ANON_PAGES};
>> + long root_stat[MEM_CGROUP_STAT_NSTATS] = {0};
>>
>> for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
>> + long val = 0;
>> +
>> if (i == MEM_CGROUP_STAT_SWAP && !do_swap_account)
>> continue;
>> +
>> + if (mem_cgroup_is_root(memcg) && (i == MEM_CGROUP_STAT_CACHE
>> + || i == MEM_CGROUP_STAT_RSS)) {
>> + val = global_page_state(global_stat[i]) -
>> + mem_cgroup_recursive_stat(memcg, i);
>> + root_stat[i] = val = val < 0 ? 0 : val;
>> + } else
>> + val = mem_cgroup_read_stat(memcg, i);
>> seq_printf(m, "%s %ld\n", mem_cgroup_stat_names[i],
>> - mem_cgroup_read_stat(memcg, i) * PAGE_SIZE);
>> + val * PAGE_SIZE);
>> }
>>
>> for (i = 0; i < MEM_CGROUP_EVENTS_NSTATS; i++)
>> @@ -5478,6 +5491,11 @@ static int memcg_stat_show(struct cgroup *cont, struct cftype *cft,
>> continue;
>> for_each_mem_cgroup_tree(mi, memcg)
>> val += mem_cgroup_read_stat(mi, i) * PAGE_SIZE;
>> +
>> + /* Adding local stats of root memcg */
>> + if (mem_cgroup_is_root(memcg))
>> + val += root_stat[i] * PAGE_SIZE;
>> +
>> seq_printf(m, "total_%s %lld\n", mem_cgroup_stat_names[i], val);
>> }
>>
>>
>
>
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