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authorMoussa A. Ba <moussa.a.ba@gmail.com>2009-09-21 17:02:29 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-22 07:17:33 -0700
commit398499d5f3613c47f2143b8c54a04efb5d7a6da9 (patch)
tree0b337ca1d0e20caa2295c159d5c0deadf362e4a0 /Documentation/filesystems
parent7103ad323b1ae32bedc3267402117e2f8b45e48d (diff)
pagemap clear_refs: modify to specify anon or mapped vma clearing
The patch makes the clear_refs more versatile in adding the option to select anonymous pages or file backed pages for clearing. This addition has a measurable impact on user space application performance as it decreases the number of pagewalks in scenarios where one is only interested in a specific type of page (anonymous or file mapped). The patch adds anonymous and file backed filters to the clear_refs interface. echo 1 > /proc/PID/clear_refs resets the bits on all pages echo 2 > /proc/PID/clear_refs resets the bits on anonymous pages only echo 3 > /proc/PID/clear_refs resets the bits on file backed pages only Any other value is ignored Signed-off-by: Moussa A. Ba <moussa.a.ba@gmail.com> Signed-off-by: Jared E. Hulbert <jaredeh@gmail.com> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/filesystems')
-rw-r--r--Documentation/filesystems/proc.txt13
1 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 1c96cb6c797..ae7f8bb1b7b 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -375,6 +375,19 @@ of memory currently marked as referenced or accessed.
This file is only present if the CONFIG_MMU kernel configuration option is
enabled.
+The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
+bits on both physical and virtual pages associated with a process.
+To clear the bits for all the pages associated with the process
+ > echo 1 > /proc/PID/clear_refs
+
+To clear the bits for the anonymous pages associated with the process
+ > echo 2 > /proc/PID/clear_refs
+
+To clear the bits for the file mapped pages associated with the process
+ > echo 3 > /proc/PID/clear_refs
+Any other value written to /proc/PID/clear_refs will have no effect.
+
+
1.2 Kernel data
---------------