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[109.81.83.158]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-378956d3765sm10691799f8f.74.2024.09.10.23.49.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Sep 2024 23:49:34 -0700 (PDT) Date: Wed, 11 Sep 2024 08:49:33 +0200 From: Michal Hocko To: Davidlohr Bueso Cc: linux-mm@kvack.org, akpm@linux-foundation.org, rientjes@google.com, yosryahmed@google.com, hannes@cmpxchg.org, almasrymina@google.com, roman.gushchin@linux.dev, gthelen@google.com, dseo3@uci.edu, a.manzanares@samsung.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH -next] mm: introduce per-node proactive reclaim interface Message-ID: References: <20240904162740.1043168-1-dave@stgolabs.net> <20240910163115.cg26kenlejlkmnsp@offworld> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240910163115.cg26kenlejlkmnsp@offworld> X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: A422F40006 X-Stat-Signature: oq1ei5ts3u4myd5yxb7m9ketxgd9y5ms X-HE-Tag: 1726037376-961864 X-HE-Meta: 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 hSuOxs2B U6QEkhG6LcGVQ7RM6PAPfR4vDqMdpS+yL0mt2b2Gagh2eAUUvOrhxrIpTuoIcn4RRGsXpu80Np/cVEaTJqvjNJtll1IDTywb5gAUMhMdv/QmtdUPe/sGlsrNkBSIXSOWUGAaSMv96FoulaogqZ4iSA1cGX0JAPbAwB0XqC54czKQboHDGBg44ioaIO/1WXU+u8ZP8lk4zVHgwfzrKgxYomu9fRejWftGrcgsOI978f8xAtpMhecIIFDlgmPMLIw/vOOpUM3xlBMTcZFcp0FfRPR8KjtEnk/fP1/pjSaFrbITsdTIbfjnGUNCpJQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000042, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue 10-09-24 09:31:15, Davidlohr Bueso wrote: > On Mon, 09 Sep 2024, Michal Hocko wrote: > > > On Wed 04-09-24 09:27:40, Davidlohr Bueso wrote: > > > 1. Users who do not use memcg can benefit from proactive reclaim. > > > > It would be great to have some specific examples here. Is there a > > specific reason memcg is not used? > > I know cases of people wanting to use this to free up fast memory > without incurring in extra latency spikes before a promotion occurs. Please give us more information about those because this might have an impact on how the interface is shaped. E.g. we might need to plan for future extension. > I do not have details as to why memcg is not used. I am not saying this is crucial to clarify but it is a natural question. We have a ready interface to achieve preemptive reclaim, why not use that and introduce something new. A plausible argument could be that memcg interface is not NUMA aware and there are usecases that are focusing on NUMA balancing rather than workload memory footprint. > I can also see > this for virtual machines running on specific nodes, reclaiming "extra" > memory based on wss and qos, as well as potential hibernation optimizations. Do not virtual solutions have own ways to manage overcommit/memory balancing (memory balooning etc.)? Does such interface fall into the existing picture? -- Michal Hocko SUSE Labs