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[173.79.56.208]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7c3e534bb1esm130728385a.31.2025.03.06.12.03.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Mar 2025 12:03:49 -0800 (PST) Date: Thu, 6 Mar 2025 15:03:46 -0500 From: Gregory Price To: Matthew Wilcox Cc: Bharata B Rao , linux-kernel@vger.kernel.org, linux-mm@kvack.org, AneeshKumar.KizhakeVeetil@arm.com, Hasan.Maruf@amd.com, Jonathan.Cameron@huawei.com, Michael.Day@amd.com, akpm@linux-foundation.org, dave.hansen@intel.com, david@redhat.com, feng.tang@intel.com, hannes@cmpxchg.org, honggyu.kim@sk.com, hughd@google.com, jhubbard@nvidia.com, k.shutemov@gmail.com, kbusch@meta.com, kmanaouil.dev@gmail.com, leesuyeon0506@gmail.com, leillc@google.com, liam.howlett@oracle.com, mgorman@techsingularity.net, mingo@redhat.com, nadav.amit@gmail.com, nphamcs@gmail.com, peterz@infradead.org, raghavendra.kt@amd.com, riel@surriel.com, rientjes@google.com, rppt@kernel.org, shivankg@amd.com, shy828301@gmail.com, sj@kernel.org, vbabka@suse.cz, weixugc@google.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, dave@stgolabs.net, yuanchu@google.com, hyeonggon.yoo@sk.com Subject: Re: [RFC PATCH 1/4] mm: migrate: Allow misplaced migration without VMA too Message-ID: References: <20250306054532.221138-1-bharata@amd.com> <20250306054532.221138-2-bharata@amd.com> 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: On Thu, Mar 06, 2025 at 06:42:10PM +0000, Matthew Wilcox wrote: > On Thu, Mar 06, 2025 at 01:19:41PM -0500, Gregory Price wrote: > > Divorced from the tiering mechanisms, is making misplaced migration able > > to migrate unmapped pages not generally useful? > > The only thing I can think of is if you have a process or set of > processes on node A calling read() and the file is cached on node B. > But in order to decide if the page is on the wrong node, you'd need > to track a lot of information about which nodes the page is being > accessed from. Which is probably why we've never bothered to do it. > > This is not a large patch for you to carry as part of your patchset. > There's nothing intrinsically wrong with it; it just has no users in > mainline and no real prospect of any being added soon. That's fair, I'm just tracking 3-4 different RFCs that are going to butt up against this, so wanted to assess whether getting the patches out ahead would save some strife. ~Gregory