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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id af79cd13be357-932de6724a4sm904385185a.43.2026.07.28.11.57.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jul 2026 11:57:16 -0700 (PDT) Date: Tue, 28 Jul 2026 14:57:10 -0400 From: Gregory Price To: Matthew Wilcox Cc: Andrew Morton , Bharata B Rao , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Jonathan.Cameron@huawei.com, dave.hansen@intel.com, mgorman@techsingularity.net, mingo@redhat.com, peterz@infradead.org, raghavendra.kt@amd.com, riel@surriel.com, rientjes@google.com, sj@kernel.org, weixugc@google.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, dave@stgolabs.net, nifan.cxl@gmail.com, xuezhengchu@huawei.com, yiannis@zptcorp.com, david@kernel.org, byungchul@sk.com, kinseyho@google.com, joshua.hahnjy@gmail.com, yuanchu@google.com, balbirs@nvidia.com, alok.rathore@samsung.com, shivankg@amd.com, donettom@linux.ibm.com Subject: Re: [PATCH v8 0/8] mm: Hot page tracking and promotion infrastructure Message-ID: References: <20260728054356.291998-1-bharata@amd.com> <20260728111401.b6d674baf8e56a27c55e0c52@linux-foundation.org> 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 Tue, Jul 28, 2026 at 07:24:46PM +0100, Matthew Wilcox wrote: > On Tue, Jul 28, 2026 at 11:14:01AM -0700, Andrew Morton wrote: > > On Tue, 28 Jul 2026 11:13:48 +0530 Bharata B Rao wrote: > > > > > This patchset introduces pghot, a subsystem for hot page tracking and > > > promotion. > > > > Can DAMON be used to do this sort of thing adequately? > > > > Thanks, I'll await review input on this. > > I don't think we should do this. I don't think it's a use-case that > customers actually want; I think it's something CPU vendors think their > customers want. I've said this repeatedly over the months this patchset > has been in development. I say no. > I've been consistent about saying we (Meta) have been actively interested in this work and helping to drive the design of it. So it's not simply something born out of a CPU vendor think tank, we're actively working on solving real problems with it. I don't have data I can share now, but I think it's fair to wait for that data before faith-merging this on the hopes it's impactful. It does make it more difficult for us to do fleet-scale testing without it being upstream, but we'll get something. Tiered memory is being deployed aggressively [0] for considerable value, and is here to stay - like it or not. ~Gregory [0] https://jovans2.github.io/files/vistara_camera_ready.pdf