mm: have zonelist contains structs with both a zone pointer and zone_idx

Filtering zonelists requires very frequent use of zone_idx().  This is costly
as it involves a lookup of another structure and a substraction operation.  As
the zone_idx is often required, it should be quickly accessible.  The node idx
could also be stored here if it was found that accessing zone->node is
significant which may be the case on workloads where nodemasks are heavily
used.

This patch introduces a struct zoneref to store a zone pointer and a zone
index.  The zonelist then consists of an array of these struct zonerefs which
are looked up as necessary.  Helpers are given for accessing the zone index as
well as the node index.

[[email protected]: Suggested struct zoneref instead of embedding information in pointers]
[[email protected]: mm-have-zonelist: fix memcg ooms]
[[email protected]: just return do_try_to_free_pages]
[[email protected]: do_try_to_free_pages gfp_mask redundant]
Signed-off-by: Mel Gorman <[email protected]>
Acked-by: Christoph Lameter <[email protected]>
Acked-by: David Rientjes <[email protected]>
Signed-off-by: Lee Schermerhorn <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Nick Piggin <[email protected]>
Signed-off-by: Hugh Dickins <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 8b35fbd8292f..a220b13cbfaf 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1967,8 +1967,8 @@ int cpuset_zonelist_valid_mems_allowed(struct zonelist *zl)
 {
 	int i;
 
-	for (i = 0; zl->zones[i]; i++) {
-		int nid = zone_to_nid(zl->zones[i]);
+	for (i = 0; zl->_zonerefs[i].zone; i++) {
+		int nid = zonelist_node_idx(&zl->_zonerefs[i]);
 
 		if (node_isset(nid, current->mems_allowed))
 			return 1;