Commit 0d16cfd4 authored by SeongJae Park's avatar SeongJae Park Committed by Linus Torvalds
Browse files

Docs/admin-guide/mm/pagemap: wordsmith page flags descriptions 

Some descriptions of page flags in 'pagemap.rst' are written in
assumption of none-rst, which respects every new line, as below:

    7 - SLAB
       page is managed by the SLAB/SLOB/SLUB/SLQB kernel memory allocator
       When compound page is used, SLUB/SLQB will only set this flag on the head

Because rst ignores the new line between the first sentence and second
sentence, resulting html looks a little bit weird, as below.

    7 - SLAB
    page is managed by the SLAB/SLOB/SLUB/SLQB kernel memory allocator When
                                                                       ^
    compound page is used, SLUB/SLQB will only set this flag on the head
    page; SLOB will not flag it at all.

This change makes it more natural and consistent with other parts in the
rendered version.

Link: https://lkml.kernel.org/r/20211022090311.3856-5-sj@kernel.org


Signed-off-by: default avatarSeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b1eee3c5

Documentation/admin-guide/mm/pagemap.rst

+27 −26
Original line number Diff line number Diff line
@@ -90,13 +90,14 @@ Short descriptions to the page flags 
====================================



0 - LOCKED

   page is being locked for exclusive access, e.g. by undergoing read/write IO

   The page is being locked for exclusive access, e.g. by undergoing read/write

   IO.

7 - SLAB

   page is managed by the SLAB/SLOB/SLUB/SLQB kernel memory allocator

   The page is managed by the SLAB/SLOB/SLUB/SLQB kernel memory allocator.

   When compound page is used, SLUB/SLQB will only set this flag on the head

   page; SLOB will not flag it at all.

10 - BUDDY

    a free memory block managed by the buddy system allocator

    A free memory block managed by the buddy system allocator.

    The buddy system organizes free memory in blocks of various orders.

    An order N block has 2^N physically contiguous pages, with the BUDDY flag

    set for and _only_ for the first page.
@@ -112,65 +113,65 @@ Short descriptions to the page flags 
16 - COMPOUND_TAIL

    A compound page tail (see description above).

17 - HUGE

    this is an integral part of a HugeTLB page

    This is an integral part of a HugeTLB page.

19 - HWPOISON

    hardware detected memory corruption on this page: don't touch the data!

    Hardware detected memory corruption on this page: don't touch the data!

20 - NOPAGE

    no page frame exists at the requested address

    No page frame exists at the requested address.

21 - KSM

    identical memory pages dynamically shared between one or more processes

    Identical memory pages dynamically shared between one or more processes.

22 - THP

    contiguous pages which construct transparent hugepages

    Contiguous pages which construct transparent hugepages.

23 - OFFLINE

    page is logically offline

    The page is logically offline.

24 - ZERO_PAGE

    zero page for pfn_zero or huge_zero page

    Zero page for pfn_zero or huge_zero page.

25 - IDLE

    page has not been accessed since it was marked idle (see

    The page has not been accessed since it was marked idle (see

    :ref:`Documentation/admin-guide/mm/idle_page_tracking.rst <idle_page_tracking>`).

    Note that this flag may be stale in case the page was accessed via

    a PTE. To make sure the flag is up-to-date one has to read

    ``/sys/kernel/mm/page_idle/bitmap`` first.

26 - PGTABLE

    page is in use as a page table

    The page is in use as a page table.



IO related page flags

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



1 - ERROR

   IO error occurred

   IO error occurred.

3 - UPTODATE

   page has up-to-date data

   The page has up-to-date data.

   ie. for file backed page: (in-memory data revision >= on-disk one)

4 - DIRTY

   page has been written to, hence contains new data

   The page has been written to, hence contains new data.

   i.e. for file backed page: (in-memory data revision >  on-disk one)

8 - WRITEBACK

   page is being synced to disk

   The page is being synced to disk.



LRU related page flags

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



5 - LRU

   page is in one of the LRU lists

   The page is in one of the LRU lists.

6 - ACTIVE

   page is in the active LRU list

   The page is in the active LRU list.

18 - UNEVICTABLE

   page is in the unevictable (non-)LRU list It is somehow pinned and

   The page is in the unevictable (non-)LRU list It is somehow pinned and

   not a candidate for LRU page reclaims, e.g. ramfs pages,

   shmctl(SHM_LOCK) and mlock() memory segments

   shmctl(SHM_LOCK) and mlock() memory segments.

2 - REFERENCED

   page has been referenced since last LRU list enqueue/requeue

   The page has been referenced since last LRU list enqueue/requeue.

9 - RECLAIM

   page will be reclaimed soon after its pageout IO completed

   The page will be reclaimed soon after its pageout IO completed.

11 - MMAP

   a memory mapped page

   A memory mapped page.

12 - ANON

   a memory mapped page that is not part of a file

   A memory mapped page that is not part of a file.

13 - SWAPCACHE

   page is mapped to swap space, i.e. has an associated swap entry

   The page is mapped to swap space, i.e. has an associated swap entry.

14 - SWAPBACKED

   page is backed by swap/RAM

   The page is backed by swap/RAM.



The page-types tool in the tools/vm directory can be used to query the

above flags.