lkml.org 
[lkml]   [2022]   [May]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [v3 PATCH 8/8] mm: mmap: register suitable readonly file vmas for khugepaged
From
On 4/4/22 22:02, Yang Shi wrote:
> 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@suse.cz/)
> 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.
>
> Reported-by: Vlastimil Babka <vbabka@suse.cz>
> Signed-off-by: Yang Shi <shy828301@gmail.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
> mm/mmap.c | 6 ++++++
> mm/shmem.c | 4 ----
> 2 files changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 604c8dece5dd..616ebbc2d052 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1842,6 +1842,12 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
> }
>
> 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)
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 92eca974771d..0c448080d210 100644
> --- a/mm/shmem.c
> +++ b/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>
> @@ -2239,7 +2238,6 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
>
> file_accessed(file);
> vma->vm_ops = &shmem_vm_ops;
> - khugepaged_enter_vma(vma, vma->vm_flags);
> return 0;
> }
>
> @@ -4132,8 +4130,6 @@ int shmem_zero_setup(struct vm_area_struct *vma)
> vma->vm_file = file;
> vma->vm_ops = &shmem_vm_ops;
>
> - khugepaged_enter_vma(vma, vma->vm_flags);
> -
> return 0;
> }
>

\
 
 \ /
  Last update: 2022-05-09 17:44    [W:0.253 / U:0.688 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site