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Tue, 05 May 2026 00:45:52 -0700 (PDT) Received: from gourry-fedora-PF4VCD3F ([213.147.98.98]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45055d36dacsm2455028f8f.32.2026.05.05.00.45.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 May 2026 00:45:51 -0700 (PDT) Date: Tue, 5 May 2026 08:45:41 +0100 From: Gregory Price To: Arun George/Arun George Cc: lsf-pc@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, damon@lists.linux.dev, kernel-team@meta.com, gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, dave@stgolabs.net, jonathan.cameron@huawei.com, dave.jiang@intel.com, alison.schofield@intel.com, vishal.l.verma@intel.com, ira.weiny@intel.com, longman@redhat.com, akpm@linux-foundation.org, david@kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, osalvador@suse.de, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, yury.norov@gmail.com, linux@rasmusvillemoes.dk, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, jackmanb@google.com, sj@kernel.org, baolin.wang@linux.alibaba.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, muchun.song@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev, jannh@google.com, linmiaohe@huawei.com, nao.horiguchi@gmail.com, pfalcato@suse.de, rientjes@google.com, shakeel.butt@linux.dev, riel@surriel.com, harry.yoo@oracle.com, cl@gentwo.org, roman.gushchin@linux.dev, chrisl@kernel.org, kasong@tencent.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, zhengqi.arch@bytedance.com, terry.bowman@amd.com, gost.dev@samsung.com, arungeorge05@gmail.com, cpgs@samsung.com Subject: Re: [LSF/MM/BPF TOPIC][RFC PATCH v4 00/27] Private Memory Nodes (w/ Compressed RAM) Message-ID: References: <20260222084842.1824063-1-gourry@gourry.net> <1983025922.01777297382206.JavaMail.epsvc@epcpadp2new> <1891546521.01777455002601.JavaMail.epsvc@epcpadp1new> <1891546521.01777901881625.JavaMail.epsvc@epcpadp2new> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1891546521.01777901881625.JavaMail.epsvc@epcpadp2new> X-Rspam-User: X-Rspamd-Queue-Id: 43F11100011 X-Rspamd-Server: rspam06 X-Stat-Signature: te7dyxijbnytuhgcpxaq16kjbydgg17u X-HE-Tag: 1777967154-271988 X-HE-Meta: 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 MaprkJZC OKSPchTq/LhsGJQ+lVIlk+s3Gk7d/X3XSjtYfK7uhvtXxCBI7hmuhYX4DU6+vDiNNu3J4LXTuaIbT4Qe9kvtV4vGZk9EzZDkzc10PNy4MFrcWyrQ2ykrZHXTgZ8YMzGcFqwqgWxR7Ot3CYFkQPPBAW6ZlPgKz7hkhwX2nXqxCKlvOCw7zKZVqos76ERVhuaJb/Tqwzs2MpF8zy8ZrnR/as2R0ttnX5iwo0RpQA7VxpPwFYHQusQNMUc1N1elizaS5wR1xvMMvb+mV+RefR4hmZtp10rLl5zLcMGXZjGoyLXUL9nwEx53thq0IehrKpcNACZd0NLhxaP2JrveRHiRVt20gnSURx53bk7YaRC8cR2aZ4qc5lwTLmZrJjCzVvvbuvUUV0ZDTxjHgTKxc6vpoYFYyIA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, May 04, 2026 at 06:38:54PM +0530, Arun George/Arun George wrote: > On 29-04-2026 07:12 pm, Gregory Price wrote: > > But I see this 'write budget' (budget in terms of number of write > operations that can be handled by the device, not capacity) to be > provided by the device in control plane; not by the workloads in the host. > In the scenario i'm talking about, a "write budget" is defined as a number of pages that are allows to be mapped writable in the page tables at any given time. > 1) We can modulate the write budget depending on the actual > compressibility in the device (and so workloads data). We don't have to > do estimation based on the workloads. > Barring the device causing backpressure to increase latency and slow down writes, modulating a write budget doesn't actually do anything useful. Once a page is mapped writable - the CPU is free to write to that page uncontended. I think a write budget is "doable" but maybe a bit optimistic for an MVP. There are many corner cases to handle, and I would prefer to see that as an experimental optimization. > 2) We don't have to do the capacity modulation - as in ballooning or > shrinker. > You still need capacity modulation in some way to respond to drops in compression ratio. ~Gregory