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Date: Thu, 28 Jul 2022 14:45:24 -0700 (PDT) From: David Rientjes <rientjes@...gle.com> To: Yosry Ahmed <yosryahmed@...gle.com> cc: Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>, Roman Gushchin <roman.gushchin@...ux.dev>, Shakeel Butt <shakeelb@...gle.com>, Muchun Song <songmuchun@...edance.com>, Andrew Morton <akpm@...ux-foundation.org>, Matthew Wilcox <willy@...radead.org>, Vlastimil Babka <vbabka@...e.cz>, David Hildenbrand <david@...hat.com>, Miaohe Lin <linmiaohe@...wei.com>, NeilBrown <neilb@...e.de>, Alistair Popple <apopple@...dia.com>, Suren Baghdasaryan <surenb@...gle.com>, Peter Xu <peterx@...hat.com>, linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, linux-mm@...ck.org Subject: Re: [PATCH v5] mm: vmpressure: don't count proactive reclaim in vmpressure 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@mail.gmail.com/ > > Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com> Acked-by: David Rientjes <rientjes@...gle.com>
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