The patch titled
doc: clarify the behaviour of dirty_ratio/dirty_bytes
has been added to the -mm tree. Its filename is
doc-clarify-the-behaviour-of-dirty_ratio-dirty_bytes.patch
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------------------------------------------------------
Subject: doc: clarify the behaviour of dirty_ratio/dirty_bytes
From: Andrea Righi <arighi@xxxxxxxxxxx>
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@xxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrea Righi <arighi@xxxxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/sysctl/vm.txt | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff -puN Documentation/sysctl/vm.txt~doc-clarify-the-behaviour-of-dirty_ratio-dirty_bytes Documentation/sysctl/vm.txt
--- a/Documentation/sysctl/vm.txt~doc-clarify-the-behaviour-of-dirty_ratio-dirty_bytes
+++ a/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
_
Patches currently in -mm which might be from arighi@xxxxxxxxxxx are
doc-clarify-the-behaviour-of-dirty_ratio-dirty_bytes.patch
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