linux-kernel - Re: [PATCH] cgroup/cpuset: Add a new isolated mems.policy type.

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Message-ID: <YxT/liaotbiOod51@slm.duckdns.org>
Date:   Sun, 4 Sep 2022 09:42:14 -1000
From:   Tejun Heo <tj@...nel.org>
To:     hezhongkun <hezhongkun.hzk@...edance.com>
Cc:     lizefan.x@...edance.com, hannes@...xchg.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cgroup/cpuset: Add a new isolated mems.policy type.

Hello,

On Fri, Sep 02, 2022 at 02:33:03PM +0800, hezhongkun wrote:
> From: Zhongkun He <hezhongkun.hzk@...edance.com>
> 
> Mempolicy is difficult to use because it is set in-process
> via a system call. We want to make it easier to use mempolicy
> in cpuset, and  we can control low-priority cgroups to
> allocate memory in specified nodes. So this patch want to
> adds the mempolicy interface in cpuset.
> 
> The mempolicy priority of cpuset is lower than the task.
> The order of getting the policy is:
> 	1) vma mempolicy
> 	2) task->mempolicy
> 	3) cpuset->mempolicy
> 	4) default policy.
> 
> cpuset's policy is owned by itself, but descendants will
> get the default mempolicy from parent.
> 
> How to use the mempolicy interface:
> 	echo prefer:2 > /sys/fs/cgroup/zz/cpuset.mems.policy
> 	echo bind:1-3 > /sys/fs/cgroup/zz/cpuset.mems.policy
>         echo interleave:0,1,2,3 >/sys/fs/cgroup/zz/cpuset.mems.policy
> Show the policy:
> 	cat /sys/fs/cgroup/zz/cpuset.mems.policy
> 		prefer:2
> 	cat /sys/fs/cgroup/zz/cpuset.mems.policy
> 		bind:1-3
> 	cat /sys/fs/cgroup/zz/cpuset.mems.policy
> 		interleave:0-3
> Clear the policy:
> 	echo default > /sys/fs/cgroup/zz/cpuset.mems.policy

So, I'm a fan of adding cgroup functionalities which don't enforce anything
resource related. What you're proposing can easily be achieved with userland
tooling, right?

Thanks.

-- 
tejun