linux-kernel - Re: [RFC][PATCH 1/2] memcg: Ensure every task that uses an mm is in the same memory cgroup

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Message-ID: <20180601191652.GZ1351649@devbig577.frc2.facebook.com>
Date:   Fri, 1 Jun 2018 12:16:52 -0700
From:   Tejun Heo <tj@...nel.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Kirill Tkhai <ktkhai@...tuozzo.com>, peterz@...radead.org,
        viro@...iv.linux.org.uk, mingo@...nel.org,
        paulmck@...ux.vnet.ibm.com, keescook@...omium.org, riel@...hat.com,
        tglx@...utronix.de, kirill.shutemov@...ux.intel.com,
        marcos.souza.org@...il.com, hoeun.ryu@...il.com,
        pasha.tatashin@...cle.com, gs051095@...il.com, dhowells@...hat.com,
        rppt@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
        Balbir Singh <balbir@...ux.vnet.ibm.com>,
        Oleg Nesterov <oleg@...hat.com>
Subject: Re: [RFC][PATCH 1/2] memcg: Ensure every task that uses an mm is in
 the same memory cgroup

Hello,

On Fri, Jun 01, 2018 at 01:11:59PM -0500, Eric W. Biederman wrote:
> Widening the definition of a process sounds good.  The memory control
> group code would still need a way to forbid these in cgroup v1 mode,
> when someone uses the task file.

Yeap, you're right.  We'll need memcg's can_attach rejecting for v1.

> Using widening instead of denying should reduce the risk of introducing
> a regression.
> 
> The only reason I support the crazy case in my earlier patch is so that
> we can have this discussion and in case we do cause a regression with
> this change the previous algorithmic cleanup won't have to be reverted
> as well.

Yeah, sure thing.

Thanks a lot.

-- 
tejun