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

[Vlastimil Babka]

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.

> [...]

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