From: Tejun Heo <tj@kernel.org>
To: Jan Kara <jack@suse.cz>
Cc: axboe@kernel.dk, hannes@cmpxchg.org, mhocko@kernel.org,
vdavydov.dev@gmail.com, cgroups@vger.kernel.org,
linux-mm@kvack.org, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel-team@fb.com, guro@fb.com,
akpm@linux-foundation.org
Subject: Re: [PATCH 4/4] writeback, memcg: Implement foreign dirty flushing
Date: Thu, 15 Aug 2019 10:31:48 -0700 [thread overview]
Message-ID: <20190815173148.GD588936@devbig004.ftw2.facebook.com> (raw)
In-Reply-To: <20190815143404.GK14313@quack2.suse.cz>
Hello, Jan.
On Thu, Aug 15, 2019 at 04:34:04PM +0200, Jan Kara wrote:
> I have to say I'm a bit nervous about the completely lockless handling
> here. I understand that garbage in the cgwb_frn will just result in this
> mechanism not working and possibly flushing wrong wb's but still it seems a
> bit fragile. But I don't see any cheap way of synchronizing this so I guess
> let's try how this will work in practice.
Yeah, this approach is fundamentally best-effort, so I went for low
overhead and mostly correct operation. If something like this doesn't
cut it (w/ bug fixes and some polishing over time), my gut feeling is
that we probably should bite the bullet and synchronize cgroup memory
and inode ownerships rather than pushing further on inherently
imprecise mitigation mechanisms.
Thanks.
--
tejun
prev parent reply other threads:[~2019-08-15 17:31 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-03 14:01 [PATCHSET] writeback, memcg: Implement foreign inode flushing Tejun Heo
2019-08-03 14:01 ` [PATCH 1/4] writeback: Generalize and expose wb_completion Tejun Heo
2019-08-15 14:41 ` Jan Kara
2019-08-03 14:01 ` [PATCH 2/4] bdi: Add bdi->id Tejun Heo
2019-08-03 15:39 ` Matthew Wilcox
2019-08-03 15:53 ` Tejun Heo
2019-08-03 16:17 ` Matthew Wilcox
2019-08-06 23:01 ` Andrew Morton
2019-08-07 18:31 ` Tejun Heo
2019-08-07 19:00 ` Andrew Morton
2019-08-07 20:34 ` Tejun Heo
2019-08-09 0:57 ` Rik van Riel
2019-08-15 14:46 ` Jan Kara
2019-08-15 17:34 ` Tejun Heo
2019-08-03 14:01 ` [PATCH 3/4] writeback, memcg: Implement cgroup_writeback_by_id() Tejun Heo
2019-08-15 14:05 ` Jan Kara
2019-08-15 15:43 ` Tejun Heo
2019-08-15 14:54 ` Jan Kara
2019-08-15 16:12 ` Tejun Heo
2019-08-03 14:01 ` [PATCH 4/4] writeback, memcg: Implement foreign dirty flushing Tejun Heo
2019-08-06 23:03 ` Andrew Morton
2019-08-07 18:34 ` Tejun Heo
2019-08-15 14:34 ` Jan Kara
2019-08-15 17:31 ` Tejun Heo [this message]
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