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

[David Miller <davem@davemloft.net>]

From: Johannes Weiner <hannes@cmpxchg.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@cmpxchg.org>

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

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