linux-kernel - Re: [RFC PATCH v4 0/3] memcg weighted interleave mempolicy control

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Message-ID: <ZVNBMW8iJIGDyp0y@tiehlicka>
Date:   Tue, 14 Nov 2023 10:43:13 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Gregory Price <gregory.price@...verge.com>
Cc:     "tj@...nel.org" <tj@...nel.org>, John Groves <john@...alactic.com>,
        Gregory Price <gourry.memverge@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "ying.huang@...el.com" <ying.huang@...el.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "lizefan.x@...edance.com" <lizefan.x@...edance.com>,
        "hannes@...xchg.org" <hannes@...xchg.org>,
        "corbet@....net" <corbet@....net>,
        "roman.gushchin@...ux.dev" <roman.gushchin@...ux.dev>,
        "shakeelb@...gle.com" <shakeelb@...gle.com>,
        "muchun.song@...ux.dev" <muchun.song@...ux.dev>,
        "jgroves@...ron.com" <jgroves@...ron.com>
Subject: Re: [RFC PATCH v4 0/3] memcg weighted interleave mempolicy control

On Fri 10-11-23 22:42:39, Gregory Price wrote:
[...]
> If I can ask, do you think it would be out of line to propose a major
> refactor to mempolicy to enable external task's the ability to change a
> running task's mempolicy *as well as* a cgroup-wide mempolicy component?

No, I actually think this is a reasonable idea. pidfd_setmempolicy is a
generally useful extension. The mempolicy code is heavily current task
based and there might be some challenges but I believe this will a)
improve the code base and b) allow more usecases.

That being said, I still believe that a cgroup based interface is a much
better choice over a global one. Cpusets seem to be a good fit as the
controller does control memory placement wrt NUMA interfaces.
-- 
Michal Hocko
SUSE Labs