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Wed, 10 Sep 2025 16:57:37 -0700 (PDT) Date: Wed, 10 Sep 2025 16:51:19 -0700 Mime-Version: 1.0 X-Mailer: git-send-email 2.51.0.384.g4c02a37b29-goog Message-ID: <20250910235121.2544928-1-kinseyho@google.com> Subject: [RFC PATCH v2 0/2] mm: multi-gen LRU scanning for page promotion From: Kinsey Ho To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Jonathan.Cameron@huawei.com, dave.hansen@intel.com, gourry@gourry.net, hannes@cmpxchg.org, 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, akpm@linux-foundation.org, david@redhat.com, byungchul@sk.com, kinseyho@google.com, joshua.hahnjy@gmail.com, yuanchu@google.com, balbirs@nvidia.com, alok.rathore@samsung.com, lorenzo.stoakes@oracle.com, axelrasmussen@google.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, zhengqi.arch@bytedance.com, shakeel.butt@linux.dev Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 80A92180002 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: udwmtg94cx4qijxnhmm93ow41x8ybeeq X-HE-Tag: 1757548659-749156 X-HE-Meta: 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 6bw5qNTK 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: This patch series introduces a software-based approach to identifying hot pages for promotion in tiered memory systems, particularly those leveraging CXL-attached memory, by utilizing the Multi-Generational LRU (MGLRU) framework. This method is designed to complement hardware-based hotness detection mechanisms like Intel PMU sampling, AMD IBS, or dedicated CXL memory monitoring units, providing a more comprehensive view of page access patterns, similar to kmmscand [1]. We propose to utilize MGLRU's existing infrastructure to provide hot page information. A key benefit here is the reuse of the MGLRU page table walk code, thus avoiding the overhead and duplication of effort involved in implementing a separate page table scanning mechanism. The working set reporting proposal [2] also reuses MGLRU's infrastructure, but focuses on cold page detection. It provides its own aging daemon, which could additionally provide hot page information by integrating this proof-of-concept. This series is based on and relies on [3] as the aggregation and promotion engine to implement the promotion policies. This is still in the RFC stage as a proof-of-concept and requires more rigorous testing. --- v2: Fixed a correctness issue during page table walk, where, on resume, one page found with the access-bit set was incorrectly not added to the pghot data structure provided by [3]. v1: https://lore.kernel.org/linux-mm/20250324220301.1273038-1-kinseyho@google.com/ --- [1] [RFC PATCH V3 00/17] mm: slowtier page promotion based on PTE A bit https://lore.kernel.org/linux-mm/20250814153307.1553061-1-raghavendra.kt@amd.com/ [2] [PATCH v4 0/9] mm: workingset reporting https://lore.kernel.org/linux-mm/20241127025728.3689245-1-yuanchu@google.com/ [3] [RFC PATCH v2 0/8] mm: Hot page tracking and promotion infrastructure https://lore.kernel.org/linux-mm/20250910144653.212066-1-bharata@amd.com/ Kinsey Ho (2): mm: mglru: generalize page table walk mm: klruscand: use mglru scanning for page promotion include/linux/mmzone.h | 5 ++ mm/Kconfig | 8 ++ mm/Makefile | 1 + mm/internal.h | 4 + mm/klruscand.c | 118 +++++++++++++++++++++++++++ mm/vmscan.c | 181 +++++++++++++++++++++++++++++++---------- 6 files changed, 272 insertions(+), 45 deletions(-) create mode 100644 mm/klruscand.c -- 2.51.0.384.g4c02a37b29-goog