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authorLee Schermerhorn <lee.schermerhorn@hp.com>2008-04-28 02:13:21 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-04-28 08:58:24 -0700
commitfc36b8d3d819047eb4d23ca079fb4d3af20ff076 (patch)
tree65ee215a6bdca1e8d4ac4b57525445d7d1829c1d /include
parent53f2556b6792ed99fde965f5e061749edd455623 (diff)
mempolicy: use MPOL_F_LOCAL to Indicate Preferred Local Policy
Now that we're using "preferred local" policy for system default, we need to make this as fast as possible. Because of the variable size of the mempolicy structure [based on size of nodemasks], the preferred_node may be in a different cacheline from the mode. This can result in accessing an extra cacheline in the normal case of system default policy. Suspect this is the cause of an observed 2-3% slowdown in page fault testing relative to kernel without this patch series. To alleviate this, use an internal mode flag, MPOL_F_LOCAL in the mempolicy flags member which is guaranteed [?] to be in the same cacheline as the mode itself. Verified that reworked mempolicy now performs slightly better on 25-rc8-mm1 for both anon and shmem segments with system default and vma [preferred local] policy. Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com> Cc: Christoph Lameter <clameter@sgi.com> Cc: David Rientjes <rientjes@google.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/mempolicy.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index 172b9c6acb9..b0fab9e8065 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -50,6 +50,7 @@ enum {
* are never OR'ed into the mode in mempolicy API arguments.
*/
#define MPOL_F_SHARED (1 << 0) /* identify shared policies */
+#define MPOL_F_LOCAL (1 << 1) /* preferred local allocation */
#ifdef __KERNEL__