Re: [PATCH] mm, memcg: Optionally disable memcg by default using Kconfig

Vlastimil Babka
2015-05-19T15:12:40Z

On 05/19/2015 04:53 PM, Michal Hocko wrote:
> On Tue 19-05-15 10:18:07, Johannes Weiner wrote:
>> CC'ing Tejun and cgroups for the generic cgroup interface part
>>
>> On Tue, May 19, 2015 at 11:40:57AM +0100, Mel Gorman wrote:
> [...]
>>> /usr/src/linux-4.0-vanilla/mm/memcontrol.c 6.6441 395842
>>> mem_cgroup_try_charge 2.950% 175781
>>
>> Ouch. Do you have a way to get the per-instruction breakdown of this?
>> This function really isn't doing much. I'll try to reproduce it here
>> too, I haven't seen such high costs with pft in the past.
>>
>>> try_charge 0.150% 8928
>>> get_mem_cgroup_from_mm 0.121% 7184
>
> Indeed! try_charge + get_mem_cgroup_from_mm which I would expect to be
> the biggest consumers here are below 10% of the mem_cgroup_try_charge.

Note that they don't explain 10% of the mem_cgroup_try_charge. They
*add* their own overhead to the overhead of mem_cgroup_try_charge
itself. Which might be what you meant but I wasn't sure.

> Other than that the function doesn't do much else than some flags
> queries and css_put...
>
> Do you have the full trace?
> Sorry for a stupid question but do inlines
> from other header files get accounted to memcontrol.c?

Yes, perf doesn't know about them so it's accounted to function where
the code physically is.

>
> [...]
>