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| author | Andrea Righi <arighi@develer.com> | 2010-10-27 15:33:31 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-10-27 18:03:08 -0700 |
| commit | abffc0207f12563f17bbde96e4cc0d9f3d7e2a53 (patch) | |
| tree | 42a2b7ea028cf0bdc2b5f2d38386507768c8fe5c /Documentation | |
| parent | e45c9effed903ba3fdbd6ef0498ee8989c35af0a (diff) | |
| download | lwn-abffc0207f12563f17bbde96e4cc0d9f3d7e2a53.tar.gz lwn-abffc0207f12563f17bbde96e4cc0d9f3d7e2a53.zip | |
doc: clarify the behaviour of dirty_ratio/dirty_bytes
When dirty_ratio or dirty_bytes is written the other parameter is disabled
and set to 0 (in dirty_bytes_handler() / dirty_ratio_handler()).
We do the same for dirty_background_ratio and dirty_background_bytes.
However, in the sysctl documentation, we say that the counterpart becomes
a function of the old value, that is not correct.
Clarify the documentation reporting the actual behaviour.
Reviewed-by: Greg Thelen <gthelen@google.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrea Righi <arighi@develer.com>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/sysctl/vm.txt | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt index b606c2c4dd37..30289fab86eb 100644 --- a/Documentation/sysctl/vm.txt +++ b/Documentation/sysctl/vm.txt @@ -80,8 +80,10 @@ dirty_background_bytes Contains the amount of dirty memory at which the pdflush background writeback daemon will start writeback. -If dirty_background_bytes is written, dirty_background_ratio becomes a function -of its value (dirty_background_bytes / the amount of dirtyable system memory). +Note: dirty_background_bytes is the counterpart of dirty_background_ratio. Only +one of them may be specified at a time. When one sysctl is written it is +immediately taken into account to evaluate the dirty memory limits and the +other appears as 0 when read. ============================================================== @@ -97,8 +99,10 @@ dirty_bytes Contains the amount of dirty memory at which a process generating disk writes will itself start writeback. -If dirty_bytes is written, dirty_ratio becomes a function of its value -(dirty_bytes / the amount of dirtyable system memory). +Note: dirty_bytes is the counterpart of dirty_ratio. Only one of them may be +specified at a time. When one sysctl is written it is immediately taken into +account to evaluate the dirty memory limits and the other appears as 0 when +read. Note: the minimum value allowed for dirty_bytes is two pages (in bytes); any value lower than this limit will be ignored and the old configuration will be |