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

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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: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
SeongJae Park 2021-11-05 13:48:19 -07:00 committed by Linus Torvalds
parent b1eee3c548
commit 0d16cfd46b
1 changed files with 27 additions and 26 deletions
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53
Documentation/admin-guide/mm/pagemap.rst
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@ -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.