[SCM] GNU Mach branch, master, updated. v1.8-657-g505ecd7b

[Samuel Thibault]

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- Log -----------------------------------------------------------------
commit 505ecd7b30fca1dc296205ff3c0dc3aff9d76e12
Author: Sergey Bugaev <bugaevc@gmail.com>
Date:   Mon Jun 26 14:26:50 2023 +0300

    Shrink struct vm_page size
    
    struct vm_page is supposed to be a "small structure", but it takes up 96
    bytes on x86_64 (to represent a 4k page). By utilizing bitfields and
    strategically reordering members to avoid excessive padding, it can be
    shrunk to 80 bytes.
    
    - page_lock and unlock_request only need to store a bitmask of
      VM_PROT_READ, VM_PROT_WRITE, and VM_PROT_EXECUTE. Even though the
      special values VM_PROT_NO_CHANGE and VM_PROT_NOTIFY are defined, they
      are not used for the two struct vm_page members.
    
    - type and seg_index both need to store one of the four possible values
      in the range from 0 to 3. Two bits are sufficient for this.
    
    - order needs to store a number from 0 to VM_PAGE_NR_FREE_LISTS (which
      is 11), or a special value VM_PAGE_ORDER_UNLISTED. Four bits are
      sufficient for this.
    
    No functional change.
    Message-Id: <20230626112656.435622-2-bugaevc@gmail.com>

-----------------------------------------------------------------------

Summary of changes:
 vm/vm_page.c     |  4 ++--
 vm/vm_page.h     | 18 ++++++++++++------
 vm/vm_resident.c |  2 +-
 3 files changed, 15 insertions(+), 9 deletions(-)


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