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authorWu Fengguang <fengguang.wu@intel.com>2009-06-16 15:32:26 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-16 19:47:38 -0700
commit17e895012f7fe9dc63144990da98c41bbc22d68f (patch)
tree430c333e2d23bf2fbf057ec9a5b3685eba217d99 /Documentation/vm/pagemap.txt
parentc9ba78e226057a1c2f19671383c496df187c02b5 (diff)
downloadlinux-17e895012f7fe9dc63144990da98c41bbc22d68f.tar.gz
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>
Diffstat (limited to 'Documentation/vm/pagemap.txt')
-rw-r--r--Documentation/vm/pagemap.txt62
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diff --git a/Documentation/vm/pagemap.txt b/Documentation/vm/pagemap.txt
index 1f1e69f72fc..600a304a828 100644
--- a/Documentation/vm/pagemap.txt
+++ b/Documentation/vm/pagemap.txt
@@ -49,6 +49,68 @@ There are three components to pagemap:
8. WRITEBACK
9. RECLAIM
10. BUDDY
+ 11. MMAP
+ 12. ANON
+ 13. SWAPCACHE
+ 14. SWAPBACKED
+ 15. COMPOUND_HEAD
+ 16. COMPOUND_TAIL
+ 16. HUGE
+ 18. UNEVICTABLE
+ 20. NOPAGE
+
+Short descriptions to the page flags:
+
+ 0. LOCKED
+ page is being locked for exclusive access, eg. by undergoing read/write IO
+
+ 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.
+
+10. BUDDY
+ 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.
+
+15. COMPOUND_HEAD
+16. COMPOUND_TAIL
+ A compound page with order N consists of 2^N physically contiguous pages.
+ A compound page with order 2 takes the form of "HTTT", where H donates its
+ head page and T donates its tail page(s). The major consumers of compound
+ pages are hugeTLB pages (Documentation/vm/hugetlbpage.txt), the SLUB etc.
+ memory allocators and various device drivers. However in this interface,
+ only huge/giga pages are made visible to end users.
+17. HUGE
+ this is an integral part of a HugeTLB page
+
+20. NOPAGE
+ no page frame exists at the requested address
+
+ [IO related page flags]
+ 1. ERROR IO error occurred
+ 3. UPTODATE 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
+ ie. for file backed page: (in-memory data revision > on-disk one)
+ 8. WRITEBACK page is being synced to disk
+
+ [LRU related page flags]
+ 5. LRU page is in one of the LRU lists
+ 6. ACTIVE page is in the active LRU list
+18. UNEVICTABLE page is in the unevictable (non-)LRU list
+ It is somehow pinned and not a candidate for LRU page reclaims,
+ eg. ramfs pages, shmctl(SHM_LOCK) and mlock() memory segments
+ 2. REFERENCED page has been referenced since last LRU list enqueue/requeue
+ 9. RECLAIM page will be reclaimed soon after its pageout IO completed
+11. MMAP a memory mapped page
+12. ANON a memory mapped page that is not part of a file
+13. SWAPCACHE page is mapped to swap space, ie. has an associated swap entry
+14. SWAPBACKED page is backed by swap/RAM
+
+The page-types tool in this directory can be used to query the above flags.
Using pagemap to do something useful: