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Mon, 28 Sep 2026 08:19:54 -0700 (PDT) Received: from spider.bream-herring.ts.net ([103.6.151.236]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2df91423df7sm43558615ad.43.2026.09.28.08.19.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Sep 2026 08:19:54 -0700 (PDT) From: Matthias Goergens To: Kairui Song Cc: Andrew Morton , Chris Li , Youngjun Park , Baoquan He , Johannes Weiner , David Hildenbrand , Michal Hocko , Shakeel Butt , Kemeng Shi , Nhat Pham , Yosry Ahmed , Barry Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-api@vger.kernel.org, Alejandro Colomar , linux-man@vger.kernel.org, Karel Zak , util-linux@vger.kernel.org, Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Simona Vetter , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, "Rafael J . Wysocki" , Pavel Machek , Catalin Marinas , Will Deacon , linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Shuah Khan , linux-kselftest@vger.kernel.org, Kairui Song Subject: Re: [RFC PATCH v2 0/4] mm/swap: reserve swap areas for deliberate offload Date: Mon, 28 Sep 2026 23:19:44 +0800 Message-ID: <20260928151944.2686626-1-matthias.goergens@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: References: <20260926045517.3458413-1-matthias.goergens@gmail.com> Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Kairui, > Just like we already have a "swappiness=" parameter in the reclaim > interface, perhaps adding a "swap.tier=" would be better and much > cleaner to achieve the same goal? Based on Youngjun's work here: > https://lore.kernel.org/all/20260916183437.2946306-1-youngjun.park@lge.com/ Thanks, I think that's the right base. I tried it: on top of Youngjun's v11, a "swap.tier=" argument to memory.reclaim is about 40 lines. In a VM with zram at a higher priority than a disk swap device, and a cgroup whose tier mask allowed only the disk, ordinary reclaim in that cgroup stayed on the disk, while memory.reclaim with "swap.tier=" pointing at zram went to zram only. What it doesn't cover yet is reclaim outside any configured cgroup: under global pressure, a cgroup nobody configured still reached the zram tier. So for v3 I'd like to add a system-wide limit on which tiers pressure reclaim may use, on top of the per-cgroup settings. I'll wait for Youngjun's v12 and build on that. Thanks, Matthias