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

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Message-ID: <20180910134845.GH10951@dhcp22.suse.cz>
Date:   Mon, 10 Sep 2018 15:48:45 +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 Fri 07-09-18 16:30:59, Shuah Khan wrote:
> On 09/07/2018 02:34 AM, Michal Hocko wrote:
> > 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. 
> 
> In addition to isolation, being able to reserve a block instead is one of the
> issues I am looking to address. Unfortunately memory cgroups won't address that
> issue.

Could you be more specific why you need reservations other than
isolation.

> 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.
> > 
> 
> Will you be able to point me to a good contact at Goggle and/or some pointers
> on finding discussion on the memory isolation. My searches on lkml came up
> short,

Well, Ying Han who used to work on memcg early days is working on a
different project. So I am not really sure.
https://lwn.net/Articles/459585/ might tell you more.
-- 
Michal Hocko
SUSE Labs