The patch titled
Subject: mm: mmap: register suitable readonly file vmas for khugepaged
has been added to the -mm tree. Its filename is
mm-mmap-register-suitable-readonly-file-vmas-for-khugepaged.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-mmap-register-suitable-readonly-file-vmas-for-khugepaged.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-mmap-register-suitable-readonly-file-vmas-for-khugepaged.patch
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------------------------------------------------------
From: Yang Shi <shy828301@xxxxxxxxx>
Subject: mm: mmap: register suitable readonly file vmas for khugepaged
The readonly FS THP relies on khugepaged to collapse THP for suitable
vmas. But it is kind of "random luck" for khugepaged to see the readonly
FS vmas
(https://lore.kernel.org/linux-mm/00f195d4-d039-3cf2-d3a1-a2c88de397a0@xxxxxxx/)
since currently the vmas are registered to khugepaged when:
- Anon huge pmd page fault
- VMA merge
- MADV_HUGEPAGE
- Shmem mmap
If the above conditions are not met, even though khugepaged is enabled it
won't see readonly FS vmas at all. MADV_HUGEPAGE could be specified
explicitly to tell khugepaged to collapse this area, but when khugepaged
mode is "always" it should scan suitable vmas as long as VM_NOHUGEPAGE is
not set.
So make sure readonly FS vmas are registered to khugepaged to make the
behavior more consistent.
Registering suitable vmas in common mmap path, that could cover both
readonly FS vmas and shmem vmas, so removed the khugepaged calls in
shmem.c.
Still need to keep the khugepaged call in vma_merge() since vma_merge() is
called in a lot of places, for example, madvise, mprotect, etc.
Link: https://lkml.kernel.org/r/20220404200250.321455-9-shy828301@xxxxxxxxx
Signed-off-by: Yang Shi <shy828301@xxxxxxxxx>
Reported-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Cc: Song Liu <song@xxxxxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mmap.c | 6 ++++++
mm/shmem.c | 4 ----
2 files changed, 6 insertions(+), 4 deletions(-)
--- a/mm/mmap.c~mm-mmap-register-suitable-readonly-file-vmas-for-khugepaged
+++ a/mm/mmap.c
@@ -1856,6 +1856,12 @@ unsigned long mmap_region(struct file *f
}
vma_link(mm, vma, prev, rb_link, rb_parent);
+
+ /*
+ * vma_merge() calls khugepaged_enter_vma() either, the below
+ * call covers the non-merge case.
+ */
+ khugepaged_enter_vma(vma, vma->vm_flags);
/* Once vma denies write, undo our temporary denial count */
unmap_writable:
if (file && vm_flags & VM_SHARED)
--- a/mm/shmem.c~mm-mmap-register-suitable-readonly-file-vmas-for-khugepaged
+++ a/mm/shmem.c
@@ -34,7 +34,6 @@
#include <linux/export.h>
#include <linux/swap.h>
#include <linux/uio.h>
-#include <linux/khugepaged.h>
#include <linux/hugetlb.h>
#include <linux/fs_parser.h>
#include <linux/swapfile.h>
@@ -2240,7 +2239,6 @@ static int shmem_mmap(struct file *file,
file_accessed(file);
vma->vm_ops = &shmem_vm_ops;
- khugepaged_enter_vma(vma, vma->vm_flags);
return 0;
}
@@ -4130,8 +4128,6 @@ int shmem_zero_setup(struct vm_area_stru
vma->vm_file = file;
vma->vm_ops = &shmem_vm_ops;
- khugepaged_enter_vma(vma, vma->vm_flags);
-
return 0;
}
_
Patches currently in -mm which might be from shy828301@xxxxxxxxx are
sched-coredumph-clarify-the-use-of-mmf_vm_hugepage.patch
mm-khugepaged-remove-redundant-check-for-vm_no_khugepaged.patch
mm-khugepaged-skip-dax-vma.patch
mm-thp-only-regular-file-could-be-thp-eligible.patch
mm-khugepaged-make-khugepaged_enter-void-function.patch
mm-khugepaged-move-some-khugepaged_-functions-to-khugepagedc.patch
mm-khugepaged-introduce-khugepaged_enter_vma-helper.patch
mm-mmap-register-suitable-readonly-file-vmas-for-khugepaged.patch
