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mm: hugetlb_vmemmap: introduce the name HVO 

It it inconvenient to mention the feature of optimizing vmemmap pages
associated with HugeTLB pages when communicating with others since there
is no specific or abbreviated name for it when it is first introduced. 
Let us give it a name HVO (HugeTLB Vmemmap Optimization) from now.

This commit also updates the document about "hugetlb_free_vmemmap" by the
way discussed in thread [1].

Link: https://lore.kernel.org/all/21aae898-d54d-cc4b-a11f-1bb7fddcfffa@redhat.com/ [1]
Link: https://lkml.kernel.org/r/20220628092235.91270-4-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Will Deacon <will@kernel.org>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Muchun Song 2022-06-28 17:22:30 +08:00 committed by Andrew Morton
parent cf5472e561
commit dff033818a
9 changed files with 23 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
Documentation/admin-guide/kernel-parameters.txt
View File

@ -1731,12 +1731,13 @@
hugetlb_free_vmemmap=
[KNL] Reguires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
enabled.
Control if HugeTLB Vmemmap Optimization (HVO) is enabled.
Allows heavy hugetlb users to free up some more
memory (7 * PAGE_SIZE for each 2MB hugetlb page).
Format: { [oO][Nn]/Y/y/1 | [oO][Ff]/N/n/0 (default) }
Format: { on | off (default) }
[oO][Nn]/Y/y/1: enable the feature
[oO][Ff]/N/n/0: disable the feature
on: enable HVO
off: disable HVO
Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
the default is on.

4
Documentation/admin-guide/mm/hugetlbpage.rst
View File

@ -164,8 +164,8 @@ default_hugepagesz
will all result in 256 2M huge pages being allocated. Valid default
huge page size is architecture dependent.
hugetlb_free_vmemmap
When CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is set, this enables optimizing
unused vmemmap pages associated with each HugeTLB page.
When CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is set, this enables HugeTLB
Vmemmap Optimization (HVO).
When multiple huge page sizes are supported, ``/proc/sys/vm/nr_hugepages``
indicates the current number of pre-allocated huge pages of the default size.

4
Documentation/admin-guide/mm/memory-hotplug.rst
View File

@ -653,8 +653,8 @@ block might fail:
- Concurrent activity that operates on the same physical memory area, such as
allocating gigantic pages, can result in temporary offlining failures.
- Out of memory when dissolving huge pages, especially when freeing unused
vmemmap pages associated with each hugetlb page is enabled.
- Out of memory when dissolving huge pages, especially when HugeTLB Vmemmap
Optimization (HVO) is enabled.
Offlining code may be able to migrate huge page contents, but may not be able
to dissolve the source huge page because it fails allocating (unmovable) pages

3
Documentation/admin-guide/sysctl/vm.rst
View File

@ -569,8 +569,7 @@ This knob is not available when the size of 'struct page' (a structure defined
in include/linux/mm_types.h) is not power of two (an unusual system config could
result in this).
Enable (set to 1) or disable (set to 0) the feature of optimizing vmemmap pages
associated with each HugeTLB page.
Enable (set to 1) or disable (set to 0) HugeTLB Vmemmap Optimization (HVO).
Once enabled, the vmemmap pages of subsequent allocation of HugeTLB pages from
buddy allocator will be optimized (7 pages per 2MB HugeTLB page and 4095 pages

2
Documentation/mm/vmemmap_dedup.rst
View File

@ -7,6 +7,8 @@ A vmemmap diet for HugeTLB and Device DAX
HugeTLB
=======
This section is to explain how HugeTLB Vmemmap Optimization (HVO) works.
The struct page structures (page structs) are used to describe a physical
page frame. By default, there is a one-to-one mapping from a page frame to
it's corresponding page struct.

12
fs/Kconfig
View File

@ -247,8 +247,7 @@ config HUGETLB_PAGE
#
# Select this config option from the architecture Kconfig, if it is preferred
# to enable the feature of minimizing overhead of struct page associated with
# each HugeTLB page.
# to enable the feature of HugeTLB Vmemmap Optimization (HVO).
#
config ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
bool
@ -259,14 +258,13 @@ config HUGETLB_PAGE_OPTIMIZE_VMEMMAP
depends on SPARSEMEM_VMEMMAP
config HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON
bool "Default optimizing vmemmap pages of HugeTLB to on"
bool "HugeTLB Vmemmap Optimization (HVO) defaults to on"
default n
depends on HUGETLB_PAGE_OPTIMIZE_VMEMMAP
help
When using HUGETLB_PAGE_OPTIMIZE_VMEMMAP, the optimizing unused vmemmap
pages associated with each HugeTLB page is default off. Say Y here
to enable optimizing vmemmap pages of HugeTLB by default. It can then
be disabled on the command line via hugetlb_free_vmemmap=off.
The HugeTLB VmemmapvOptimization (HVO) defaults to off. Say Y here to
enable HVO by default. It can be disabled via hugetlb_free_vmemmap=off
(boot command line) or hugetlb_optimize_vmemmap (sysctl).
config MEMFD_CREATE
def_bool TMPFS || HUGETLBFS

3
include/linux/page-flags.h
View File

@ -208,8 +208,7 @@ enum pageflags {
DECLARE_STATIC_KEY_FALSE(hugetlb_optimize_vmemmap_key);
/*
* If the feature of optimizing vmemmap pages associated with each HugeTLB
* page is enabled, the head vmemmap page frame is reused and all of the tail
* If HVO is enabled, the head vmemmap page frame is reused and all of the tail
* vmemmap addresses map to the head vmemmap page frame (furture details can
* refer to the figure at the head of the mm/hugetlb_vmemmap.c). In other
* words, there are more than one page struct with PG_head associated with each

8
mm/hugetlb_vmemmap.c
View File

@ -1,8 +1,8 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Optimize vmemmap pages associated with HugeTLB
* HugeTLB Vmemmap Optimization (HVO)
*
* Copyright (c) 2020, Bytedance. All rights reserved.
* Copyright (c) 2020, ByteDance. All rights reserved.
*
* Author: Muchun Song <songmuchun@bytedance.com>
*
@ -156,8 +156,8 @@ void __init hugetlb_vmemmap_init(struct hstate *h)
/*
* There are only (RESERVE_VMEMMAP_SIZE / sizeof(struct page)) struct
* page structs that can be used when CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP,
* so add a BUILD_BUG_ON to catch invalid usage of the tail struct page.
* page structs that can be used when HVO is enabled, add a BUILD_BUG_ON
* to catch invalid usage of the tail page structs.
*/
BUILD_BUG_ON(__NR_USED_SUBPAGE >=
RESERVE_VMEMMAP_SIZE / sizeof(struct page));

4
mm/hugetlb_vmemmap.h
View File

@ -1,8 +1,8 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Optimize vmemmap pages associated with HugeTLB
* HugeTLB Vmemmap Optimization (HVO)
*
* Copyright (c) 2020, Bytedance. All rights reserved.
* Copyright (c) 2020, ByteDance. All rights reserved.
*
* Author: Muchun Song <songmuchun@bytedance.com>
*/