linux-kernel - [PATCH v1 0/1] Improved Memory Tier Creation for CPUless NUMA Nodes

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Message-Id: <20240301082248.3456086-1-horenchuang@bytedance.com>
Date: Fri,  1 Mar 2024 08:22:44 +0000
From: "Ho-Ren (Jack) Chuang" <horenchuang@...edance.com>
To: "Hao Xiang" <hao.xiang@...edance.com>,
	"Gregory Price" <gourry.memverge@...il.com>,
	aneesh.kumar@...ux.ibm.com,
	mhocko@...e.com,
	tj@...nel.org,
	john@...alactic.com,
	"Eishan Mirakhur" <emirakhur@...ron.com>,
	"Vinicius Tavares Petrucci" <vtavarespetr@...ron.com>,
	"Ravis OpenSrc" <Ravis.OpenSrc@...ron.com>,
	"Alistair Popple" <apopple@...dia.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Jiang <dave.jiang@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Huang Ying <ying.huang@...el.com>,
	"Ho-Ren (Jack) Chuang" <horenchuang@...edance.com>,
	linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Cc: "Ho-Ren (Jack) Chuang" <horenc@...edu>,
	"Ho-Ren (Jack) Chuang" <horenchuang@...il.com>,
	linux-cxl@...r.kernel.org,
	qemu-devel@...gnu.org
Subject: [PATCH v1 0/1] Improved Memory Tier Creation for CPUless NUMA Nodes

The memory tiering component in the kernel is functionally useless for
CPUless memory/non-DRAM devices like CXL1.1 type3 memory because the nodes
are lumped together in the DRAM tier.
https://lore.kernel.org/linux-mm/PH0PR08MB7955E9F08CCB64F23963B5C3A860A@PH0PR08MB7955.namprd08.prod.outlook.com/T/

This patchset automatically resolves the issues. It delays the initialization
of memory tiers for CPUless NUMA nodes until they obtain HMAT information
at boot time, eliminating the need for user intervention.
If no HMAT specified, it falls back to using `default_dram_type`.

Example usecase:
We have CXL memory on the host, and we create VMs with a new system memory
device backed by host CXL memory. We inject CXL memory performance attributes
through QEMU, and the guest now sees memory nodes with performance attributes
in HMAT. With this change, we enable the guest kernel to construct
the correct memory tiering for the memory nodes.

Ho-Ren (Jack) Chuang (1):
  memory tier: acpi/hmat: create CPUless memory tiers after obtaining
    HMAT info

 drivers/acpi/numa/hmat.c     |  3 ++
 include/linux/memory-tiers.h |  6 +++
 mm/memory-tiers.c            | 76 ++++++++++++++++++++++++++++++++----
 3 files changed, 77 insertions(+), 8 deletions(-)

-- 
Hao Xiang and Ho-Ren (Jack) Chuang