aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorWu Fengguang <fengguang.wu@intel.com>2009-06-16 18:32:26 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-16 22:47:38 -0400
commit17e895012f7fe9dc63144990da98c41bbc22d68f (patch)
tree430c333e2d23bf2fbf057ec9a5b3685eba217d99
parentc9ba78e226057a1c2f19671383c496df187c02b5 (diff)
pagemap: document 9 more exported page flags
Also add short descriptions for all of the 20 exported page flags. Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Matt Mackall <mpm@selenic.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--Documentation/vm/pagemap.txt62
1 files changed, 62 insertions, 0 deletions
diff --git a/Documentation/vm/pagemap.txt b/Documentation/vm/pagemap.txt
index 1f1e69f72fcd..600a304a828c 100644
--- a/Documentation/vm/pagemap.txt
+++ b/Documentation/vm/pagemap.txt
@@ -49,6 +49,68 @@ There are three components to pagemap:
49 8. WRITEBACK 49 8. WRITEBACK
50 9. RECLAIM 50 9. RECLAIM
51 10. BUDDY 51 10. BUDDY
52 11. MMAP
53 12. ANON
54 13. SWAPCACHE
55 14. SWAPBACKED
56 15. COMPOUND_HEAD
57 16. COMPOUND_TAIL
58 16. HUGE
59 18. UNEVICTABLE
60 20. NOPAGE
61
62Short descriptions to the page flags:
63
64 0. LOCKED
65 page is being locked for exclusive access, eg. by undergoing read/write IO
66
67 7. SLAB
68 page is managed by the SLAB/SLOB/SLUB/SLQB kernel memory allocator
69 When compound page is used, SLUB/SLQB will only set this flag on the head
70 page; SLOB will not flag it at all.
71
7210. BUDDY
73 a free memory block managed by the buddy system allocator
74 The buddy system organizes free memory in blocks of various orders.
75 An order N block has 2^N physically contiguous pages, with the BUDDY flag
76 set for and _only_ for the first page.
77
7815. COMPOUND_HEAD
7916. COMPOUND_TAIL
80 A compound page with order N consists of 2^N physically contiguous pages.
81 A compound page with order 2 takes the form of "HTTT", where H donates its
82 head page and T donates its tail page(s). The major consumers of compound
83 pages are hugeTLB pages (Documentation/vm/hugetlbpage.txt), the SLUB etc.
84 memory allocators and various device drivers. However in this interface,
85 only huge/giga pages are made visible to end users.
8617. HUGE
87 this is an integral part of a HugeTLB page
88
8920. NOPAGE
90 no page frame exists at the requested address
91
92 [IO related page flags]
93 1. ERROR IO error occurred
94 3. UPTODATE page has up-to-date data
95 ie. for file backed page: (in-memory data revision >= on-disk one)
96 4. DIRTY page has been written to, hence contains new data
97 ie. for file backed page: (in-memory data revision > on-disk one)
98 8. WRITEBACK page is being synced to disk
99
100 [LRU related page flags]
101 5. LRU page is in one of the LRU lists
102 6. ACTIVE page is in the active LRU list
10318. UNEVICTABLE page is in the unevictable (non-)LRU list
104 It is somehow pinned and not a candidate for LRU page reclaims,
105 eg. ramfs pages, shmctl(SHM_LOCK) and mlock() memory segments
106 2. REFERENCED page has been referenced since last LRU list enqueue/requeue
107 9. RECLAIM page will be reclaimed soon after its pageout IO completed
10811. MMAP a memory mapped page
10912. ANON a memory mapped page that is not part of a file
11013. SWAPCACHE page is mapped to swap space, ie. has an associated swap entry
11114. SWAPBACKED page is backed by swap/RAM
112
113The page-types tool in this directory can be used to query the above flags.
52 114
53Using pagemap to do something useful: 115Using pagemap to do something useful:
54 116