Memoryless nodes: Use N_HIGH_MEMORY for cpusets
cpusets try to ensure that any node added to a cpuset's mems_allowed is
on-line and contains memory. The assumption was that online nodes contained
memory. Thus, it is possible to add memoryless nodes to a cpuset and then add
tasks to this cpuset. This results in continuous series of oom-kill and
apparent system hang.
Change cpusets to use node_states[N_HIGH_MEMORY] [a.k.a. node_memory_map] in
place of node_online_map when vetting memories. Return error if admin
attempts to write a non-empty mems_allowed node mask containing only
memoryless-nodes.
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Bob Picco <bob.picco@hp.com>
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mel@skynet.ie>
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/cpusets.txt b/Documentation/cpusets.txt
index f2c0a68..b875d23 100644
--- a/Documentation/cpusets.txt
+++ b/Documentation/cpusets.txt
@@ -35,7 +35,8 @@
----------------------
Cpusets provide a mechanism for assigning a set of CPUs and Memory
-Nodes to a set of tasks.
+Nodes to a set of tasks. In this document "Memory Node" refers to
+an on-line node that contains memory.
Cpusets constrain the CPU and Memory placement of tasks to only
the resources within a tasks current cpuset. They form a nested
@@ -220,8 +221,8 @@
The cpus and mems files in the root (top_cpuset) cpuset are
read-only. The cpus file automatically tracks the value of
cpu_online_map using a CPU hotplug notifier, and the mems file
-automatically tracks the value of node_online_map using the
-cpuset_track_online_nodes() hook.
+automatically tracks the value of node_states[N_MEMORY]--i.e.,
+nodes with memory--using the cpuset_track_online_nodes() hook.
1.4 What are exclusive cpusets ?
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 826b15e..9e633ea 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -93,7 +93,7 @@
return node_possible_map;
}
-#define cpuset_current_mems_allowed (node_online_map)
+#define cpuset_current_mems_allowed (node_states[N_HIGH_MEMORY])
static inline void cpuset_init_current_mems_allowed(void) {}
static inline void cpuset_update_task_memory_state(void) {}
#define cpuset_nodes_subset_current_mems_allowed(nodes) (1)
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 57e6448..8b2daac 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -581,26 +581,28 @@
/*
* Return in *pmask the portion of a cpusets's mems_allowed that
- * are online. If none are online, walk up the cpuset hierarchy
- * until we find one that does have some online mems. If we get
- * all the way to the top and still haven't found any online mems,
- * return node_online_map.
+ * are online, with memory. If none are online with memory, walk
+ * up the cpuset hierarchy until we find one that does have some
+ * online mems. If we get all the way to the top and still haven't
+ * found any online mems, return node_states[N_HIGH_MEMORY].
*
* One way or another, we guarantee to return some non-empty subset
- * of node_online_map.
+ * of node_states[N_HIGH_MEMORY].
*
* Call with callback_mutex held.
*/
static void guarantee_online_mems(const struct cpuset *cs, nodemask_t *pmask)
{
- while (cs && !nodes_intersects(cs->mems_allowed, node_online_map))
+ while (cs && !nodes_intersects(cs->mems_allowed,
+ node_states[N_HIGH_MEMORY]))
cs = cs->parent;
if (cs)
- nodes_and(*pmask, cs->mems_allowed, node_online_map);
+ nodes_and(*pmask, cs->mems_allowed,
+ node_states[N_HIGH_MEMORY]);
else
- *pmask = node_online_map;
- BUG_ON(!nodes_intersects(*pmask, node_online_map));
+ *pmask = node_states[N_HIGH_MEMORY];
+ BUG_ON(!nodes_intersects(*pmask, node_states[N_HIGH_MEMORY]));
}
/**
@@ -924,7 +926,10 @@
int fudge;
int retval;
- /* top_cpuset.mems_allowed tracks node_online_map; it's read-only */
+ /*
+ * top_cpuset.mems_allowed tracks node_stats[N_HIGH_MEMORY];
+ * it's read-only
+ */
if (cs == &top_cpuset)
return -EACCES;
@@ -941,8 +946,21 @@
retval = nodelist_parse(buf, trialcs.mems_allowed);
if (retval < 0)
goto done;
+ if (!nodes_intersects(trialcs.mems_allowed,
+ node_states[N_HIGH_MEMORY])) {
+ /*
+ * error if only memoryless nodes specified.
+ */
+ retval = -ENOSPC;
+ goto done;
+ }
}
- nodes_and(trialcs.mems_allowed, trialcs.mems_allowed, node_online_map);
+ /*
+ * Exclude memoryless nodes. We know that trialcs.mems_allowed
+ * contains at least one node with memory.
+ */
+ nodes_and(trialcs.mems_allowed, trialcs.mems_allowed,
+ node_states[N_HIGH_MEMORY]);
oldmem = cs->mems_allowed;
if (nodes_equal(oldmem, trialcs.mems_allowed)) {
retval = 0; /* Too easy - nothing to do */
@@ -2098,8 +2116,9 @@
/*
* The cpus_allowed and mems_allowed nodemasks in the top_cpuset track
- * cpu_online_map and node_online_map. Force the top cpuset to track
- * whats online after any CPU or memory node hotplug or unplug event.
+ * cpu_online_map and node_states[N_HIGH_MEMORY]. Force the top cpuset to
+ * track what's online after any CPU or memory node hotplug or unplug
+ * event.
*
* To ensure that we don't remove a CPU or node from the top cpuset
* that is currently in use by a child cpuset (which would violate
@@ -2119,7 +2138,7 @@
guarantee_online_cpus_mems_in_subtree(&top_cpuset);
top_cpuset.cpus_allowed = cpu_online_map;
- top_cpuset.mems_allowed = node_online_map;
+ top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY];
mutex_unlock(&callback_mutex);
mutex_unlock(&manage_mutex);
@@ -2147,8 +2166,9 @@
#ifdef CONFIG_MEMORY_HOTPLUG
/*
- * Keep top_cpuset.mems_allowed tracking node_online_map.
- * Call this routine anytime after you change node_online_map.
+ * Keep top_cpuset.mems_allowed tracking node_states[N_HIGH_MEMORY].
+ * Call this routine anytime after you change
+ * node_states[N_HIGH_MEMORY].
* See also the previous routine cpuset_handle_cpuhp().
*/
@@ -2167,7 +2187,7 @@
void __init cpuset_init_smp(void)
{
top_cpuset.cpus_allowed = cpu_online_map;
- top_cpuset.mems_allowed = node_online_map;
+ top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY];
hotcpu_notifier(cpuset_handle_cpuhp, 0);
}
@@ -2309,7 +2329,7 @@
*
* Description: Returns the nodemask_t mems_allowed of the cpuset
* attached to the specified @tsk. Guaranteed to return some non-empty
- * subset of node_online_map, even if this means going outside the
+ * subset of node_states[N_HIGH_MEMORY], even if this means going outside the
* tasks cpuset.
**/