The patch titled
Subject: mm/huge_memory: prevent THP_ZERO_PAGE_ALLOC increased twice
has been added to the -mm mm-unstable branch. Its filename is
mm-huge_memory-prevent-thp_zero_page_alloc-increased-twice.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-huge_memory-prevent-thp_zero_page_alloc-increased-twice.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Liu Shixin <liushixin2@xxxxxxxxxx>
Subject: mm/huge_memory: prevent THP_ZERO_PAGE_ALLOC increased twice
Date: Fri, 9 Sep 2022 10:16:53 +0800
A user who reads THP_ZERO_PAGE_ALLOC may be more concerned about the huge
zero pages that are really allocated for thp. It is misleading to
increase THP_ZERO_PAGE_ALLOC twice if two threads call get_huge_zero_page
concurrently. Don't increase the value if the huge page is not really
used.
Update Documentation/admin-guide/mm/transhuge.rst to suit.
Link: https://lkml.kernel.org/r/20220909021653.3371879-1-liushixin2@xxxxxxxxxx
Signed-off-by: Liu Shixin <liushixin2@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/mm/transhuge.rst | 7 +++----
mm/huge_memory.c | 2 +-
2 files changed, 4 insertions(+), 5 deletions(-)
--- a/Documentation/admin-guide/mm/transhuge.rst~mm-huge_memory-prevent-thp_zero_page_alloc-increased-twice
+++ a/Documentation/admin-guide/mm/transhuge.rst
@@ -366,10 +366,9 @@ thp_split_pmd
page table entry.
thp_zero_page_alloc
- is incremented every time a huge zero page is
- successfully allocated. It includes allocations which where
- dropped due race with other allocation. Note, it doesn't count
- every map of the huge zero page, only its allocation.
+ is incremented every time a huge zero page used for thp is
+ successfully allocated. Note, it doesn't count every map of
+ the huge zero page, only its allocation.
thp_zero_page_alloc_failed
is incremented if kernel fails to allocate
--- a/mm/huge_memory.c~mm-huge_memory-prevent-thp_zero_page_alloc-increased-twice
+++ a/mm/huge_memory.c
@@ -163,7 +163,6 @@ retry:
count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
return false;
}
- count_vm_event(THP_ZERO_PAGE_ALLOC);
preempt_disable();
if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
preempt_enable();
@@ -175,6 +174,7 @@ retry:
/* We take additional reference here. It will be put back by shrinker */
atomic_set(&huge_zero_refcount, 2);
preempt_enable();
+ count_vm_event(THP_ZERO_PAGE_ALLOC);
return true;
}
_
Patches currently in -mm which might be from liushixin2@xxxxxxxxxx are
mm-thp-simplify-has_transparent_hugepage-by-using-is_builtin.patch
mm-thp-remove-redundant-config_transparent_hugepage.patch
mm-kmemleak-make-create_object-return-void.patch
mm-shuffle-convert-module_param_call-to-module_param_cb.patch
mm-kfence-convert-to-define_seq_attribute.patch
mm-huge_memory-prevent-thp_zero_page_alloc-increased-twice.patch
