Re: [PATCH 4/4] memcg: always enable kmemcg on the default hierarchy

[Tejun Heo <tj@kernel.org>]

Hello,

On Tue, Sep 01, 2015 at 02:44:59PM +0200, Michal Hocko wrote:
> The runtime overhead is not negligible and I do not see why everybody
> should be paying that price by default. I can definitely see the reason why
> somebody would want to enable the kmem accounting but many users will
> probably never care because the kernel footprint would be in the noise
> wrt. user memory.

We said the same thing about hierarchy support.  Sure, it's not the
same but I think it's wiser to keep the architectural decisions at a
higher level.  I don't think kmem overhead is that high but if this
actually is a problem we'd need a per-cgroup knob anyway.

> > We wanna put all memory consumptions under the same roof by default.
> 
> But I am not sure we will ever achieve this. E.g. hugetlb memory is way
> too different to be under the same charging by default IMO. Also all
> the random drivers calling into the page allocator directly in the user
> context would need to charge explicitly.

Oh I meant the big ones.  I don't think we'll achieve 100% coverage
either but even just catching the major ones, kmem and tcp socket
buffers, should remove most ambiguities around memory consumption.

Thanks.

-- 
tejun

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