On Thu, Aug 22, 2024 at 03:25:43PM GMT, Liam R. Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
>
> The vma_munmap_struct has a hole of 4 bytes and pushes the struct to
> three cachelines. Relocating the three booleans upwards allows for the
> struct to only use two cachelines (as reported by pahole on amd64).
>
> Before:
> struct vma_munmap_struct {
> struct vma_iterator * vmi; /* 0 8 */
> struct vm_area_struct * vma; /* 8 8 */
> struct vm_area_struct * prev; /* 16 8 */
> struct vm_area_struct * next; /* 24 8 */
> struct list_head * uf; /* 32 8 */
> long unsigned int start; /* 40 8 */
> long unsigned int end; /* 48 8 */
> long unsigned int unmap_start; /* 56 8 */
> /* --- cacheline 1 boundary (64 bytes) --- */
> long unsigned int unmap_end; /* 64 8 */
> int vma_count; /* 72 4 */
>
> /* XXX 4 bytes hole, try to pack */
>
> long unsigned int nr_pages; /* 80 8 */
> long unsigned int locked_vm; /* 88 8 */
> long unsigned int nr_accounted; /* 96 8 */
> long unsigned int exec_vm; /* 104 8 */
> long unsigned int stack_vm; /* 112 8 */
> long unsigned int data_vm; /* 120 8 */
> /* --- cacheline 2 boundary (128 bytes) --- */
> bool unlock; /* 128 1 */
> bool clear_ptes; /* 129 1 */
> bool closed_vm_ops; /* 130 1 */
>
> /* size: 136, cachelines: 3, members: 19 */
> /* sum members: 127, holes: 1, sum holes: 4 */
> /* padding: 5 */
> /* last cacheline: 8 bytes */
> };
>
> After:
> struct vma_munmap_struct {
> struct vma_iterator * vmi; /* 0 8 */
> struct vm_area_struct * vma; /* 8 8 */
> struct vm_area_struct * prev; /* 16 8 */
> struct vm_area_struct * next; /* 24 8 */
> struct list_head * uf; /* 32 8 */
> long unsigned int start; /* 40 8 */
> long unsigned int end; /* 48 8 */
> long unsigned int unmap_start; /* 56 8 */
> /* --- cacheline 1 boundary (64 bytes) --- */
> long unsigned int unmap_end; /* 64 8 */
> int vma_count; /* 72 4 */
> bool unlock; /* 76 1 */
> bool clear_ptes; /* 77 1 */
> bool closed_vm_ops; /* 78 1 */
>
> /* XXX 1 byte hole, try to pack */
>
> long unsigned int nr_pages; /* 80 8 */
> long unsigned int locked_vm; /* 88 8 */
> long unsigned int nr_accounted; /* 96 8 */
> long unsigned int exec_vm; /* 104 8 */
> long unsigned int stack_vm; /* 112 8 */
> long unsigned int data_vm; /* 120 8 */
>
> /* size: 128, cachelines: 2, members: 19 */
> /* sum members: 127, holes: 1, sum holes: 1 */
> };
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
> ---
> mm/vma.h | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/mm/vma.h b/mm/vma.h
> index 7047fedce459..c774642697a0 100644
> --- a/mm/vma.h
> +++ b/mm/vma.h
> @@ -40,15 +40,16 @@ struct vma_munmap_struct {
> unsigned long unmap_start; /* Unmap PTE start */
> unsigned long unmap_end; /* Unmap PTE end */
> int vma_count; /* Number of vmas that will be removed */
> + bool unlock; /* Unlock after the munmap */
> + bool clear_ptes; /* If there are outstanding PTE to be cleared */
> + bool closed_vm_ops; /* call_mmap() was encountered, so vmas may be closed */
> + /* 1 byte hole */
> unsigned long nr_pages; /* Number of pages being removed */
> unsigned long locked_vm; /* Number of locked pages */
> unsigned long nr_accounted; /* Number of VM_ACCOUNT pages */
> unsigned long exec_vm;
> unsigned long stack_vm;
> unsigned long data_vm;
> - bool unlock; /* Unlock after the munmap */
> - bool clear_ptes; /* If there are outstanding PTE to be cleared */
> - bool closed_vm_ops; /* call_mmap() was encountered, so vmas may be closed */
> };
>
> #ifdef CONFIG_DEBUG_VM_MAPLE_TREE
> --
> 2.43.0
>
