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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 /mm/mempolicy.c
parent53f2556b6792ed99fde965f5e061749edd455623 (diff)
downloadvexpress-lsk-fc36b8d3d819047eb4d23ca079fb4d3af20ff076.tar.gz
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 'mm/mempolicy.c')
-rw-r--r--mm/mempolicy.c47
1 files changed, 22 insertions, 25 deletions
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 7b3ae977b15..143b019e983 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -110,7 +110,7 @@ enum zone_type policy_zone = 0;
struct mempolicy default_policy = {
.refcnt = ATOMIC_INIT(1), /* never free it */
.mode = MPOL_PREFERRED,
- .v = { .preferred_node = -1 },
+ .flags = MPOL_F_LOCAL,
};
static const struct mempolicy_operations {
@@ -163,7 +163,7 @@ static int mpol_new_interleave(struct mempolicy *pol, const nodemask_t *nodes)
static int mpol_new_preferred(struct mempolicy *pol, const nodemask_t *nodes)
{
if (!nodes)
- pol->v.preferred_node = -1; /* local allocation */
+ pol->flags |= MPOL_F_LOCAL; /* local allocation */
else if (nodes_empty(*nodes))
return -EINVAL; /* no allowed nodes */
else
@@ -290,14 +290,15 @@ static void mpol_rebind_preferred(struct mempolicy *pol,
if (pol->flags & MPOL_F_STATIC_NODES) {
int node = first_node(pol->w.user_nodemask);
- if (node_isset(node, *nodes))
+ if (node_isset(node, *nodes)) {
pol->v.preferred_node = node;
- else
- pol->v.preferred_node = -1;
+ pol->flags &= ~MPOL_F_LOCAL;
+ } else
+ pol->flags |= MPOL_F_LOCAL;
} else if (pol->flags & MPOL_F_RELATIVE_NODES) {
mpol_relative_nodemask(&tmp, &pol->w.user_nodemask, nodes);
pol->v.preferred_node = first_node(tmp);
- } else if (pol->v.preferred_node != -1) {
+ } else if (!(pol->flags & MPOL_F_LOCAL)) {
pol->v.preferred_node = node_remap(pol->v.preferred_node,
pol->w.cpuset_mems_allowed,
*nodes);
@@ -645,7 +646,7 @@ static void get_policy_nodemask(struct mempolicy *p, nodemask_t *nodes)
*nodes = p->v.nodes;
break;
case MPOL_PREFERRED:
- if (p->v.preferred_node >= 0)
+ if (!(p->flags & MPOL_F_LOCAL))
node_set(p->v.preferred_node, *nodes);
/* else return empty node mask for local allocation */
break;
@@ -1324,13 +1325,12 @@ static nodemask_t *policy_nodemask(gfp_t gfp, struct mempolicy *policy)
/* Return a zonelist indicated by gfp for node representing a mempolicy */
static struct zonelist *policy_zonelist(gfp_t gfp, struct mempolicy *policy)
{
- int nd;
+ int nd = numa_node_id();
switch (policy->mode) {
case MPOL_PREFERRED:
- nd = policy->v.preferred_node;
- if (nd < 0)
- nd = numa_node_id();
+ if (!(policy->flags & MPOL_F_LOCAL))
+ nd = policy->v.preferred_node;
break;
case MPOL_BIND:
/*
@@ -1339,16 +1339,13 @@ static struct zonelist *policy_zonelist(gfp_t gfp, struct mempolicy *policy)
* current node is part of the mask, we use the zonelist for
* the first node in the mask instead.
*/
- nd = numa_node_id();
if (unlikely(gfp & __GFP_THISNODE) &&
unlikely(!node_isset(nd, policy->v.nodes)))
nd = first_node(policy->v.nodes);
break;
case MPOL_INTERLEAVE: /* should not happen */
- nd = numa_node_id();
break;
default:
- nd = 0;
BUG();
}
return node_zonelist(nd, gfp);
@@ -1379,14 +1376,15 @@ static unsigned interleave_nodes(struct mempolicy *policy)
*/
unsigned slab_node(struct mempolicy *policy)
{
- if (!policy)
+ if (!policy || policy->flags & MPOL_F_LOCAL)
return numa_node_id();
switch (policy->mode) {
case MPOL_PREFERRED:
- if (unlikely(policy->v.preferred_node >= 0))
- return policy->v.preferred_node;
- return numa_node_id();
+ /*
+ * handled MPOL_F_LOCAL above
+ */
+ return policy->v.preferred_node;
case MPOL_INTERLEAVE:
return interleave_nodes(policy);
@@ -1666,7 +1664,8 @@ int __mpol_equal(struct mempolicy *a, struct mempolicy *b)
case MPOL_INTERLEAVE:
return nodes_equal(a->v.nodes, b->v.nodes);
case MPOL_PREFERRED:
- return a->v.preferred_node == b->v.preferred_node;
+ return a->v.preferred_node == b->v.preferred_node &&
+ a->flags == b->flags;
default:
BUG();
return 0;
@@ -1946,7 +1945,7 @@ void numa_default_policy(void)
}
/*
- * "local" is pseudo-policy: MPOL_PREFERRED with preferred_node == -1
+ * "local" is pseudo-policy: MPOL_PREFERRED with MPOL_F_LOCAL flag
* Used only for mpol_to_str()
*/
#define MPOL_LOCAL (MPOL_INTERLEAVE + 1)
@@ -1962,7 +1961,6 @@ static inline int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
{
char *p = buffer;
int l;
- int nid;
nodemask_t nodes;
unsigned short mode;
unsigned short flags = pol ? pol->flags : 0;
@@ -1979,11 +1977,10 @@ static inline int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
case MPOL_PREFERRED:
nodes_clear(nodes);
- nid = pol->v.preferred_node;
- if (nid < 0)
+ if (flags & MPOL_F_LOCAL)
mode = MPOL_LOCAL; /* pseudo-policy */
else
- node_set(nid, nodes);
+ node_set(pol->v.preferred_node, nodes);
break;
case MPOL_BIND:
@@ -2004,7 +2001,7 @@ static inline int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
strcpy(p, policy_types[mode]);
p += l;
- if (flags) {
+ if (flags & MPOL_MODE_FLAGS) {
int need_bar = 0;
if (buffer + maxlen < p + 2)