linux-kernel - Re: [RFC] Making memcg track ownership per address_space or anon

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Message-ID: <CALYGNiMgpU51vNr186x6h-uh_9NqaTqZ_a2L60XG0STozy=30g@mail.gmail.com>
Date:	Thu, 12 Feb 2015 02:15:29 +0400
From:	Konstantin Khlebnikov <koct9i@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Greg Thelen <gthelen@...gle.com>,
	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Cgroups <cgroups@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jan Kara <jack@...e.cz>, Dave Chinner <david@...morbit.com>,
	Jens Axboe <axboe@...nel.dk>,
	Christoph Hellwig <hch@...radead.org>,
	Li Zefan <lizefan@...wei.com>, Hugh Dickins <hughd@...gle.com>
Subject: Re: [RFC] Making memcg track ownership per address_space or anon_vma

On Thu, Feb 12, 2015 at 1:05 AM, Tejun Heo <tj@...nel.org> wrote:
> On Thu, Feb 12, 2015 at 01:57:04AM +0400, Konstantin Khlebnikov wrote:
>> On Thu, Feb 12, 2015 at 12:46 AM, Tejun Heo <tj@...nel.org> wrote:
>> > Hello,
>> >
>> > On Thu, Feb 12, 2015 at 12:22:34AM +0300, Konstantin Khlebnikov wrote:
>> >> > Yeah, available memory to the matching memcg and the number of dirty
>> >> > pages in it.  It's gonna work the same way as the global case just
>> >> > scoped to the cgroup.
>> >>
>> >> That might be a problem: all dirty pages accounted to cgroup must be
>> >> reachable for its own personal writeback or balanace-drity-pages will be
>> >> unable to satisfy memcg dirty memory thresholds. I've done accounting
>> >
>> > Yeah, it would.  Why wouldn't it?
>>
>> How do you plan to do per-memcg/blkcg writeback for balance-dirty-pages?
>> Or you're thinking only about separating writeback flow into blkio cgroups
>> without actual inode filtering? I mean delaying inode writeback and keeping
>> dirty pages as long as possible if their cgroups are far from threshold.
>
> What?  The code was already in the previous patchset.  I'm just gonna
> rip out the code to handle inode being dirtied on multiple wb's.

Well, ok. Even if shared writes are rare whey should be handled somehow
without relying on kupdate-like writeback. If memcg has a lot of dirty pages
but their inodes are accidentially belong to wrong wb queues when tasks in
that memcg shouldn't stuck in balance-dirty-pages until somebody outside
acidentially writes this data. That's all what I wanted to say.

>
> --
> tejun
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