Re: [PATCH v5] mm: vmpressure: don't count proactive reclaim in vmpressure

[David Rientjes]

On Thu, 21 Jul 2022, Yosry Ahmed wrote:

> memory.reclaim is a cgroup v2 interface that allows users to
> proactively reclaim memory from a memcg, without real memory pressure.
> Reclaim operations invoke vmpressure, which is used:
> (a) To notify userspace of reclaim efficiency in cgroup v1, and
> (b) As a signal for a memcg being under memory pressure for networking
> (see mem_cgroup_under_socket_pressure()).
> 
> For (a), vmpressure notifications in v1 are not affected by this change
> since memory.reclaim is a v2 feature.
> 
> For (b), the effects of the vmpressure signal (according to Shakeel [1])
> are as follows:
> 1. Reducing send and receive buffers of the current socket.
> 2. May drop packets on the rx path.
> 3. May throttle current thread on the tx path.
> 
> Since proactive reclaim is invoked directly by userspace, not by
> memory pressure, it makes sense not to throttle networking. Hence,
> this change makes sure that proactive reclaim caused by memory.reclaim
> does not trigger vmpressure.
> 
> [1] https://lore.kernel.org/lkml/CALvZod68WdrXEmBpOkadhB5GPYmCXaDZzXH=yyGOCAjFRn4NDQ@xxxxxxxxxxxxxx/
> 
> Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>

Acked-by: David Rientjes <rientjes@xxxxxxxxxx>