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/
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>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index bab2b0b..8c06271 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -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.

diff --git a/Documentation/admin-guide/mm/hugetlbpage.rst b/Documentation/admin-guide/mm/hugetlbpage.rst
index a90330d..8e2727d 100644 (file)
--- a/Documentation/admin-guide/mm/hugetlbpage.rst
+++ b/Documentation/admin-guide/mm/hugetlbpage.rst
@@ -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.

diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentation/admin-guide/mm/memory-hotplug.rst
index 0f56ecd..a3c9e8a 100644 (file)
--- a/Documentation/admin-guide/mm/memory-hotplug.rst
+++ b/Documentation/admin-guide/mm/memory-hotplug.rst
@@ -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

diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst
index f74f722..9b833e4 100644 (file)
--- a/Documentation/admin-guide/sysctl/vm.rst
+++ b/Documentation/admin-guide/sysctl/vm.rst
@@ -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

diff --git a/Documentation/mm/vmemmap_dedup.rst b/Documentation/mm/vmemmap_dedup.rst
index c9c495f..7d7a161 100644 (file)
--- a/Documentation/mm/vmemmap_dedup.rst
+++ b/Documentation/mm/vmemmap_dedup.rst
@@ -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.

diff --git a/fs/Kconfig b/fs/Kconfig
index 5976eb3..a547307 100644 (file)
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -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

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index b44cc24..78ed46a 100644 (file)
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -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

diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index e5b83a2..bcafd9d 100644 (file)
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -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));

diff --git a/mm/hugetlb_vmemmap.h b/mm/hugetlb_vmemmap.h
index 109b0a5..ba66fad 100644 (file)
--- a/mm/hugetlb_vmemmap.h
+++ b/mm/hugetlb_vmemmap.h
@@ -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>
  */