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

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Message-ID: <YxWbBYZKDTrkmlOe@dhcp22.suse.cz>
Date:   Mon, 5 Sep 2022 08:45:25 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     hezhongkun <hezhongkun.hzk@...edance.com>
Cc:     hannes@...xchg.org, roman.gushchin@...ux.dev,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-mm@...ck.org, lizefan.x@...edance.com,
        wuyun.abel@...edance.com
Subject: Re: [PATCH] cgroup/cpuset: Add a new isolated mems.policy type.

On Sun 04-09-22 12:02:41, 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.

What is the hierarchical behavior of the policy? Say parent has a
stronger requirement (say bind) than a child (prefer)?
 
> 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

Am I just confused or did you really mean to combine all these
together?
-- 
Michal Hocko
SUSE Labs