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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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240910163115.cg26kenlejlkmnsp@offworld> 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