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[100.36.248.188]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8bf3a33f723sm95071336d6.24.2026.05.11.07.38.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 May 2026 07:38:24 -0700 (PDT) Date: Mon, 11 May 2026 10:38:22 -0400 From: Gregory Price To: Bharata B Rao Cc: Andrew Morton , 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, willy@infradead.org, 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 v7 0/7] mm: Hot page tracking and promotion infrastructure Message-ID: References: <20260504060924.344313-1-bharata@amd.com> <5110e313-8c1e-4f73-b77f-68d20c2046c8@amd.com> <20260508181812.d2ab17b08529f17b330e157c@linux-foundation.org> <893081eb-d747-458d-b6c6-86fb04bdd5b9@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: <893081eb-d747-458d-b6c6-86fb04bdd5b9@amd.com> On Mon, May 11, 2026 at 04:07:16PM +0530, Bharata B Rao wrote: > > The entire point of this patchset is not just about improving the performance. > It is mainly about adding a new dedicated infrastructure for detecting and > promoting hot pages. It is about having a subsystem that can act as a single > source of truth page hotness in the kernel. Though we aren't there yet, we have > started by having a minimal infrastructure that centralizes the hot page > promotion and associated heuristics that currently sits in scheduler so that the > same can be used with other page hotness sources as well. > The goal of hotness tracking in general is to improve performance. The goal of PGHot should be a reasonable baseline for the kernel to course-correct LRU inversions across tiers over time, because LRU threads only scan invidiual nodes and don't compare across nodes. I would hazard against trying to wholesale state it "Shall be the single source of truth", as we will inevitably discover some condition which is not covered / cannot be captured / we will simply get it wrong. Plus, intuitively, counter-balancing LRU/MGLRU aging is probably as good good as we can get without having to inject per-workload information into the system - at which point the users should use DAMON. ~Gregory