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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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <893081eb-d747-458d-b6c6-86fb04bdd5b9@amd.com> X-Rspam-User: X-Rspamd-Queue-Id: 5D4BA1C000D X-Rspamd-Server: rspam06 X-Stat-Signature: uukb6u9sefx71mn8j8akymwxckdra836 X-HE-Tag: 1778510306-32529 X-HE-Meta: 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 6NNnDjr4 SsRzzdBDBYGpqZXH+9VEF2vU9qG5XzvbBbwXhRxM6TYLCmOt4fv2bvauZ8iHGXCqHE5lT6L8/48C1bSjLOuI6sL+cqXPJs8H2PCglRHHSFq+xZVPuumpYs9j0UgNshr01U9Cwny5XIOmFXdDLVvQGD7A7eFxB9lNm+j4q6ayblxTowrImUxJbzIeCBP9ji71pjiCYHAuNO7Y12833nZfeAq7Fsa0o7WkavKtRmEoFsa1VZJjDoGBW2QmWEmKaXX9BD8xq+Yy4GwGAPTqs2PCTW0R4j43gtB0OCWbHd2LWGiHKxb74KkyDcptLlNh0nsMzCrawAQOydvzy5yZ3mKkjQpqGUmIKN5hF3u1LE+xnZiBL2MgLjmGLTh2M5ys9Hjq1v15wEcyuIz8FiuDebT2eVA2smChDp4PZs7XzRxLqRNCSDh/SUy72SrJyWEnVr9m4ng+7 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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