forked from luck/tmp_suning_uos_patched
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>
This commit is contained in:
parent
c9ba78e226
commit
17e895012f
|
@ -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:
|
||||
|
||||
|
|
Loading…
Reference in New Issue
Block a user