Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 20 Feb 2020 13:35:52 -0500
From:   Chris Down <chris@chrisdown.name>
To:     Dan Schatzberg <schatzberg.dan@gmail.com>
Cc:     Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>,
        Li Zefan <lizefan@huawei.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>, Roman Gushchin <guro@fb.com>,
        Shakeel Butt <shakeelb@google.com>,
        Yang Shi <yang.shi@linux.alibaba.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        "open list:BLOCK LAYER" <linux-block@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        "open list:CONTROL GROUP (CGROUP)" <cgroups@vger.kernel.org>,
        "open list:CONTROL GROUP - MEMORY RESOURCE CONTROLLER (MEMCG)" 
        <linux-mm@kvack.org>
Subject: Re: [PATCH v3 2/3] mm: Charge active memcg when no mm is set
Message-ID: <20200220183552.GA2181061@chrisdown.name>
References: <cover.1582216294.git.schatzberg.dan@gmail.com>
 <0a27b6fcbd1f7af104d7f4cf0adc6a31e0e7dd19.1582216294.git.schatzberg.dan@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Disposition: inline
In-Reply-To: <0a27b6fcbd1f7af104d7f4cf0adc6a31e0e7dd19.1582216294.git.schatzberg.dan@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Dan Schatzberg writes:
>memalloc_use_memcg() worked for kernel allocations but was silently
>ignored for user pages.
>
>This patch establishes a precedence order for who gets charged:
>
>1. If there is a memcg associated with the page already, that memcg is
>   charged. This happens during swapin.
>
>2. If an explicit mm is passed, mm->memcg is charged. This happens
>   during page faults, which can be triggered in remote VMs (eg gup).
>
>3. Otherwise consult the current process context. If it has configured
>   a current->active_memcg, use that. Otherwise, current->mm->memcg.
>
>Previously, if a NULL mm was passed to mem_cgroup_try_charge (case 3) it
>would always charge the root cgroup. Now it looks up the current
>active_memcg first (falling back to charging the root cgroup if not
>set).
>
>Signed-off-by: Dan Schatzberg <schatzberg.dan@gmail.com>
>Acked-by: Johannes Weiner <hannes@cmpxchg.org>
>Acked-by: Tejun Heo <tj@kernel.org>

Acked-by: Chris Down <chris@chrisdown.name>

Thanks! The clarification the v2 thread for this made things clear to me.