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Commit 7a6560e0 authored by Andrea Righi's avatar Andrea Righi Committed by Linus Torvalds
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documentation: clarify dirty_ratio and dirty_background_ratio description 



The current documentation of dirty_ratio and dirty_background_ratio is a
bit misleading.

In the documentation we say that they are "a percentage of total system
memory", but the current page writeback policy, intead, is to apply the
percentages to the dirtyable memory, that means free pages + reclaimable
pages.

Better to be more explicit to clarify this concept.

Signed-off-by: default avatarAndrea Righi <righi.andrea@gmail.com>
Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9f1b16a5

Documentation/filesystems/proc.txt

+8 −5
Original line number Diff line number Diff line
@@ -1384,15 +1384,18 @@ causes the kernel to prefer to reclaim dentries and inodes. 
dirty_background_ratio

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



Contains, as a percentage of total system memory, the number of pages at which

the pdflush background writeback daemon will start writing out dirty data.

Contains, as a percentage of the dirtyable system memory (free pages + mapped

pages + file cache, not including locked pages and HugePages), the number of

pages at which the pdflush background writeback daemon will start writing out

dirty data.



dirty_ratio

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



Contains, as a percentage of total system memory, the number of pages at which

a process which is generating disk writes will itself start writing out dirty

data.

Contains, as a percentage of the dirtyable system memory (free pages + mapped

pages + file cache, not including locked pages and HugePages), the number of

pages at which a process which is generating disk writes will itself start

writing out dirty data.



dirty_writeback_centisecs

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