linux-kernel - Re: [PATCH RFC] memcg: revert kmem.tcp accounting

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Message-ID: <20140912171809.GA24469@dhcp22.suse.cz>
Date:	Fri, 12 Sep 2014 19:18:09 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Vladimir Davydov <vdavydov@...allels.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	cgroups@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	Li Zefan <lizefan@...wei.com>,
	"David S. Miller" <davem@...emloft.net>,
	Johannes Weiner <hannes@...xchg.org>,
	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Glauber Costa <glommer@...il.com>,
	Pavel Emelianov <xemul@...allels.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Thelen <gthelen@...gle.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH RFC] memcg: revert kmem.tcp accounting

On Fri 12-09-14 19:26:58, Vladimir Davydov wrote:
> memory.kmem.tcp.limit_in_bytes works as the system-wide tcp_mem sysctl,
> but per memory cgroup. While the existence of the latter is justified
> (it prevents the system from becoming unusable due to uncontrolled tcp
> buffers growth) the reason why we need such a knob in containers isn't
> clear to me.

Parallels was the primary driver for this change. I haven't heard of
anybody using the feature other than Parallels. I also remember there
was a strong push for this feature before it was merged besides there
were some complains at the time. I do not remember details (and I am
one half way gone for the weekend now) so I do not have pointers to
discussions.

I would love to get rid of the code and I am pretty sure that networking
people would love this go even more. I didn't plan to provide kmem.tcp.*
knobs for the cgroups v2 interface but getting rid of it altogether
sounds even better. I am just not sure whether some additional users
grown over time.
Nevertheless I am really curious. What has changed that Parallels is not
interested in kmem.tcp anymore?

[...]

Anyway, more than welcome
Acked-by: Michal Hocko <mhocko@...e.cz>

In case we happened to grow more users, which I hope hasn't happened, we
would need to keep this around at least with the legacy cgroups API.
-- 
Michal Hocko
SUSE Labs
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