linux-kernel - Re: [PATCH 04/14] net: tcp_memcontrol: remove bogus hierarchy pressure propagation

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Date:	Fri, 20 Nov 2015 12:07:25 +0300
From:	Vladimir Davydov <vdavydov@...tuozzo.com>
To:	Johannes Weiner <hannes@...xchg.org>
CC:	David Miller <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>, Michal Hocko <mhocko@...e.cz>,
	<netdev@...r.kernel.org>, <linux-mm@...ck.org>,
	<cgroups@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<kernel-team@...com>
Subject: Re: [PATCH 04/14] net: tcp_memcontrol: remove bogus hierarchy
 pressure propagation

On Thu, Nov 12, 2015 at 06:41:23PM -0500, Johannes Weiner wrote:
> When a cgroup currently breaches its socket memory limit, it enters
> memory pressure mode for itself and its *ancestors*. This throttles
> transmission in unrelated sibling and cousin subtrees that have
> nothing to do with the breached limit.
> 
> On the contrary, breaching a limit should make that group and its
> *children* enter memory pressure mode. But this happens already,
> albeit lazily: if an ancestor limit is breached, siblings will enter
> memory pressure on their own once the next packet arrives for them.

Hmm, we still call sk_prot->enter_memory_pressure, which might hurt a
workload in the root cgroup AFAICS. Strange. You fix it in patch 8
though.

> 
> So no additional hierarchy code is needed. Remove the bogus stuff.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Reviewed-by: Vladimir Davydov <vdavydov@...tuozzo.com>
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