+ mm-hugetlb-introduce-a-new-config-hugetlb_page_free_vmemmap.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP
has been added to the -mm tree.  Its filename is
     mm-hugetlb-introduce-a-new-config-hugetlb_page_free_vmemmap.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-hugetlb-introduce-a-new-config-hugetlb_page_free_vmemmap.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlb-introduce-a-new-config-hugetlb_page_free_vmemmap.patch

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------------------------------------------------------
From: Muchun Song <songmuchun@bytedance.com>
Subject: mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP

The option HUGETLB_PAGE_FREE_VMEMMAP allows for the freeing of some
vmemmap pages associated with pre-allocated HugeTLB pages.  For example,
on X86_64 6 vmemmap pages of size 4KB each can be saved for each 2MB
HugeTLB page.  4094 vmemmap pages of size 4KB each can be saved for each
1GB HugeTLB page.

When a HugeTLB page is allocated or freed, the vmemmap array representing
the range associated with the page will need to be remapped.  When a page
is allocated, vmemmap pages are freed after remapping.  When a page is
freed, previously discarded vmemmap pages must be allocated before
remapping.

The config option is introduced early so that supporting code can be
written to depend on the option.  The initial version of the code only
provides support for x86-64.

Like other code which frees vmemmap, this config option depends on
HAVE_BOOTMEM_INFO_NODE.  The routine register_page_bootmem_info() is used
to register bootmem info.  Therefore, make sure register_page_bootmem_info
is enabled if HUGETLB_PAGE_FREE_VMEMMAP is defined.

Link: https://lkml.kernel.org/r/20210308102807.59745-3-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Tested-by: Chen Huang <chenhuang5@huawei.com>
Tested-by: Bodeddula Balasubramaniam <bodeddub@amazon.com>
Reviewed-by: Balbir Singh <bsingharora@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Oliver Neukum <oneukum@suse.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/x86/mm/init_64.c |    2 +-
 fs/Kconfig            |    6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

--- a/arch/x86/mm/init_64.c~mm-hugetlb-introduce-a-new-config-hugetlb_page_free_vmemmap
+++ a/arch/x86/mm/init_64.c
@@ -1264,7 +1264,7 @@ static struct kcore_list kcore_vsyscall;
 
 static void __init register_page_bootmem_info(void)
 {
-#ifdef CONFIG_NUMA
+#if defined(CONFIG_NUMA) || defined(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP)
 	int i;
 
 	for_each_online_node(i)
--- a/fs/Kconfig~mm-hugetlb-introduce-a-new-config-hugetlb_page_free_vmemmap
+++ a/fs/Kconfig
@@ -236,6 +236,12 @@ config HUGETLBFS
 config HUGETLB_PAGE
 	def_bool HUGETLBFS
 
+config HUGETLB_PAGE_FREE_VMEMMAP
+	def_bool HUGETLB_PAGE
+	depends on X86_64
+	depends on SPARSEMEM_VMEMMAP
+	depends on HAVE_BOOTMEM_INFO_NODE
+
 config MEMFD_CREATE
 	def_bool TMPFS || HUGETLBFS
 
_

Patches currently in -mm which might be from songmuchun@bytedance.com are

mm-memcontrol-fix-kernel-stack-account.patch
mm-memory_hotplug-factor-out-bootmem-core-functions-to-bootmem_infoc.patch
mm-hugetlb-introduce-a-new-config-hugetlb_page_free_vmemmap.patch
mm-hugetlb-free-the-vmemmap-pages-associated-with-each-hugetlb-page.patch
mm-hugetlb-alloc-the-vmemmap-pages-associated-with-each-hugetlb-page.patch
mm-hugetlb-set-the-pagehwpoison-to-the-raw-error-page.patch
mm-hugetlb-add-a-kernel-parameter-hugetlb_free_vmemmap.patch
mm-hugetlb-introduce-nr_free_vmemmap_pages-in-the-struct-hstate.patch
mm-hugetlb-gather-discrete-indexes-of-tail-page.patch
mm-hugetlb-optimize-the-code-with-the-help-of-the-compiler.patch