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: <20180604184738.GB1351649@devbig577.frc2.facebook.com>
Date:   Mon, 4 Jun 2018 11:47:38 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>, 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, Michal.

On Mon, Jun 04, 2018 at 03:01:19PM +0200, Michal Hocko wrote:
> > 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.
> 
> Do we really need? I mean, do we know about any existing usecase that
> would need this weird threading concept and depend on memory migration
> which doesn't really work?

I thought the requirement is from the ->owner change so that the
association doesn't become 1:N, right?

Thanks.

-- 
tejun