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>
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 1c96cb6..ae7f8bb 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -375,6 +375,19 @@
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
---------------