PATCH 10/15 - Mempolicy: MPOL_PREFERRED cleanups for "local allocation"
Against: 2.6.25-rc8-mm1
V4 -> V5:
+ change mpol_to_str() to show "local" policy for MPOL_PREFERRED with
preferred_node == -1. libnuma wrappers and numactl use the term
"local allocation", so let's use it here.
V3 -> V4:
+ updated Documentation/vm/numa_memory_policy.txt to better explain
[I think] the "local allocation" feature of MPOL_PREFERRED.
V2 -> V3:
+ renamed get_nodemask() to get_policy_nodemask() to more closely
match what it's doing.
V1 -> V2:
+ renamed get_zonemask() to get_nodemask(). Mel Gorman suggested this
was a valid "cleanup".
Here are a couple of "cleanups" for MPOL_PREFERRED behavior
when v.preferred_node < 0 -- i.e., "local allocation":
1) [do_]get_mempolicy() calls the now renamed get_policy_nodemask()
to fetch the nodemask associated with a policy. Currently,
get_policy_nodemask() returns the set of nodes with memory, when
the policy 'mode' is 'PREFERRED, and the preferred_node is < 0.
Change to return an empty nodemask, as this is what was specified
to achieve "local allocation".
2) When a task is moved into a [new] cpuset, mpol_rebind_policy() is
called to adjust any task and vma policy nodes to be valid in the
new cpuset. However, when the policy is MPOL_PREFERRED, and the
preferred_node is <0, no rebind is necessary. The "local allocation"
indication is valid in any cpuset. Existing code will "do the right
thing" because node_remap() will just return the argument node when
it is outside of the valid range of node ids. However, I think it is
clearer and cleaner to skip the remap explicitly in this case.
3) mpol_to_str() produces a printable, "human readable" string from a
struct mempolicy. For MPOL_PREFERRED with preferred_node <0, show
"local", as this indicates local allocation, as the task migrates
among nodes. Note that this matches the usage of "local allocation"
in libnuma() and numactl. Without this change, I believe that node_set()
[via set_bit()] will set bit 31, resulting in a misleading display.
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@xxxxxx>
mm/mempolicy.c | 28 ++++++++++++++++++----------
1 file changed, 18 insertions(+), 10 deletions(-)
Index: linux-2.6.25-rc8-mm1/mm/mempolicy.c
===================================================================
--- linux-2.6.25-rc8-mm1.orig/mm/mempolicy.c 2008-04-02 17:47:37.000000000 -0400
+++ linux-2.6.25-rc8-mm1/mm/mempolicy.c 2008-04-02 17:47:41.000000000 -0400
@@ -645,11 +645,9 @@ static void get_policy_nodemask(struct m
*nodes = p->v.nodes;
break;
case MPOL_PREFERRED:
- /* or use current node instead of memory_map? */
- if (p->v.preferred_node < 0)
- *nodes = node_states[N_HIGH_MEMORY];
- else
+ if (p->v.preferred_node >= 0)
node_set(p->v.preferred_node, *nodes);
+ /* else return empty node mask for local allocation */
break;
default:
BUG();
@@ -804,7 +802,7 @@ int do_migrate_pages(struct mm_struct *m
int err = 0;
nodemask_t tmp;
- down_read(&mm->mmap_sem);
+ down_read(&mm->mmap_sem);
err = migrate_vmas(mm, from_nodes, to_nodes, flags);
if (err)
@@ -1949,10 +1947,12 @@ void numa_default_policy(void)
}
/*
- * Display pages allocated per node and memory policy via /proc.
+ * "local" is pseudo-policy: MPOL_PREFERRED with preferred_node == -1
+ * Used only for mpol_to_str()
*/
+#define MPOL_LOCAL (MPOL_INTERLEAVE + 1)
static const char * const policy_types[] =
- { "default", "prefer", "bind", "interleave" };
+ { "default", "prefer", "bind", "interleave", "local" };
/*
* Convert a mempolicy into a string.
@@ -1963,6 +1963,7 @@ static inline int mpol_to_str(char *buff
{
char *p = buffer;
int l;
+ int nid;
nodemask_t nodes;
unsigned short mode;
unsigned short flags = pol ? pol->flags : 0;
@@ -1979,7 +1980,11 @@ static inline int mpol_to_str(char *buff
case MPOL_PREFERRED:
nodes_clear(nodes);
- node_set(pol->v.preferred_node, nodes);
+ nid = pol->v.preferred_node;
+ if (nid < 0)
+ mode = MPOL_LOCAL; /* pseudo-policy */
+ else
+ node_set(nid, nodes);
break;
case MPOL_BIND:
@@ -1994,8 +1999,8 @@ static inline int mpol_to_str(char *buff
}
l = strlen(policy_types[mode]);
- if (buffer + maxlen < p + l + 1)
- return -ENOSPC;
+ if (buffer + maxlen < p + l + 1)
+ return -ENOSPC;
strcpy(p, policy_types[mode]);
p += l;
@@ -2094,6 +2099,9 @@ static inline void check_huge_range(stru
}
#endif
+/*
+ * Display pages allocated per node and memory policy via /proc.
+ */
int show_numa_map(struct seq_file *m, void *v)
{
struct proc_maps_private *priv = m->private;
--
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