linux-kernel - Re: [PATCH 13/13] mm: memcontrol: hook up vmpressure to socket pressure

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Message-Id: <20151125.113048.45218641761530031.davem@davemloft.net>
Date:	Wed, 25 Nov 2015 11:30:48 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	hannes@...xchg.org
Cc:	akpm@...ux-foundation.org, vdavydov@...tuozzo.com, mhocko@...e.cz,
	tj@...nel.org, eric.dumazet@...il.com, netdev@...r.kernel.org,
	linux-mm@...ck.org, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH 13/13] mm: memcontrol: hook up vmpressure to socket
 pressure

From: Johannes Weiner <hannes@...xchg.org>
Date: Tue, 24 Nov 2015 16:59:40 -0500

> Let the networking stack know when a memcg is under reclaim pressure
> so that it can clamp its transmit windows accordingly.
> 
> Whenever the reclaim efficiency of a cgroup's LRU lists drops low
> enough for a MEDIUM or HIGH vmpressure event to occur, assert a
> pressure state in the socket and tcp memory code that tells it to curb
> consumption growth from sockets associated with said control group.
> 
> Traditionally, vmpressure reports for the entire subtree of a memcg
> under pressure, which drops useful information on the individual
> groups reclaimed. However, it's too late to change the userinterface,
> so add a second reporting mode that reports on the level of reclaim
> instead of at the level of pressure, and use that report for sockets.
> 
> vmpressure events are naturally edge triggered, so for hysteresis
> assert socket pressure for a second to allow for subsequent vmpressure
> events to occur before letting the socket code return to normal.
> 
> This will likely need finetuning for a wider variety of workloads, but
> for now stick to the vmpressure presets and keep hysteresis simple.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Acked-by: David S. Miller <davem@...emloft.net>
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