linux-kernel - [RFC PATCH v1 0/2] mm: multi-gen LRU scanning for page promotion

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Message-ID: <20250324220301.1273038-1-kinseyho@google.com>
Date: Mon, 24 Mar 2025 15:02:59 -0700
From: Kinsey Ho <kinseyho@...gle.com>
To: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc: yuanchu@...gle.com, AneeshKumar.KizhakeVeetil@....com, Hasan.Maruf@....com, 
	Jonathan.Cameron@...wei.com, Michael.Day@....com, akpm@...ux-foundation.org, 
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	ying.huang@...ux.alibaba.com, ziy@...dia.com, dave@...olabs.net, 
	hyeonggon.yoo@...com, bharata@....com, Kinsey Ho <kinseyho@...gle.com>
Subject: [RFC PATCH v1 0/2] mm: multi-gen LRU scanning for page promotion

This patch series introduces a software-based approach to identify
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 relies on kpromoted [3] as the migration engine to implement
the promotion policies. This is just an early proof-of-concept RFC
posted now in the context of LSFMM.

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            | 177 ++++++++++++++++++++++++++++++-----------
 6 files changed, 267 insertions(+), 46 deletions(-)
 create mode 100644 mm/klruscand.c

-- 
2.49.0.395.g12beb8f557-goog