linux-kernel - Re: [PATCH] arm64: add NUMA emulation support

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Date:   Fri, 7 Sep 2018 10:34:52 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Shuah Khan <shuah@...nel.org>
Cc:     Will Deacon <will.deacon@....com>, catalin.marinas@....com,
        sudeep.holla@....com, ganapatrao.kulkarni@...ium.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: add NUMA emulation support

On Thu 06-09-18 15:53:34, Shuah Khan wrote:
[...]
> A few critical allocations could be satisfied and root cgroup prevails. It is not the
> intent to have exclusivity at the expense of the kernel.

Well, it is not "few critical allocations". It can be a lot of
memory. Basically any GFP_KERNEL allocation. So how exactly you expect
this to work when you cannot estimate how much
memory will kernel eat?

> 
> This feature will allow a way to configure cpusets on non-NUMA for workloads that can
> benefit from the reservation and isolation that is available within the constraints of
> exclusive cpuset policies.

AFAIR this was the first approach Google took for the memory isolation
and they moved over to memory cgroups. I would recommend to talk to
those guys bebfore you introduce potentially a lot of code that will not
really work for the workload you indend it for.
-- 
Michal Hocko
SUSE Labs