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

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Message-ID: <ZU6KiRv7iy/cUY7N@memverge.com>
Date:   Fri, 10 Nov 2023 14:54:49 -0500
From:   Gregory Price <gregory.price@...verge.com>
To:     "Huang, Ying" <ying.huang@...el.com>
Cc:     Gregory Price <gourry.memverge@...il.com>,
        linux-kernel@...r.kernel.org, linux-cxl@...r.kernel.org,
        linux-mm@...ck.org, cgroups@...r.kernel.org,
        linux-doc@...r.kernel.org, akpm@...ux-foundation.org,
        mhocko@...nel.org, tj@...nel.org, lizefan.x@...edance.com,
        hannes@...xchg.org, corbet@....net, roman.gushchin@...ux.dev,
        shakeelb@...gle.com, muchun.song@...ux.dev
Subject: Re: [RFC PATCH v4 0/3] memcg weighted interleave mempolicy control

On Fri, Nov 10, 2023 at 02:16:05PM +0800, Huang, Ying wrote:
> Gregory Price <gourry.memverge@...il.com> writes:
> 
> > This patchset implements weighted interleave and adds a new cgroup
> > sysfs entry: cgroup/memory.interleave_weights (excluded from root).
> >
> > The il_weight of a node is used by mempolicy to implement weighted
> > interleave when `numactl --interleave=...` is invoked.  By default
> > il_weight for a node is always 1, which preserves the default round
> > robin interleave behavior.
> 
> IIUC, this makes it almost impossible to set the default weight of a
> node from the node memory bandwidth information.  This will make the
> life of users a little harder.
> 
> If so, how about use a new memory policy mode, for example
> MPOL_WEIGHTED_INTERLEAVE, etc.
>

weights are also inherited from parent cgroups, so if you set them in
parent slices you can automatically set update system settings.

by default the parent slice weights will always be 1 until set
otherwise.  Once they're set, children inherit naturally.

Maybe there's an argument here for including interleave_weights in the
root cgroup.

~Gregory