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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> 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: <1891546521.01777901881625.JavaMail.epsvc@epcpadp2new> 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