powerpc/pseries: CMO unused page hinting

Adds support for the "unused" page hint which can be used in shared
memory partitions to flag pages not in use, which will then be stolen
before active pages by the hypervisor when memory needs to be moved to
LPARs in need of additional memory.  Failure to mark pages as 'unused'
makes the LPAR slower to give up unused memory to other partitions.

This adds the kernel parameter 'cmo_free_hint' to disable this
functionality.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Robert Jennings <rcj@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index e87bdbfbcc75..844e9a654d0b 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -497,6 +497,13 @@ and is between 256 and 4096 characters. It is defined in the file
                         Also note the kernel might malfunction if you disable
                         some critical bits.
 
+        cmo_free_hint=  [PPC] Format: { yes | no }
+                        Specify whether pages are marked as being inactive
+                        when they are freed.  This is used in CMO environments
+                        to determine OS memory pressure for page stealing by
+                        a hypervisor.
+                        Default: yes
+
         code_bytes      [X86] How many bytes of object code to print
                         in an oops report.
                         Range: 0 - 8192