Commit 0e1e7c7a authored by Christoph Lameter's avatar Christoph Lameter Committed by Linus Torvalds
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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: default avatarLee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: default avatarBob Picco <bob.picco@hp.com>
Signed-off-by: default avatarNishanth Aravamudan <nacc@us.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mel@skynet.ie>
Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 523b9458

Documentation/cpusets.txt

+4 −3
Original line number Diff line number Diff line
@@ -35,7 +35,8 @@ CONTENTS: 
----------------------



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 @@ and name space for cpusets, with a minimum of additional kernel code. 
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 ?

include/linux/cpuset.h

+1 −1
Original line number Diff line number Diff line
@@ -93,7 +93,7 @@ static inline nodemask_t cpuset_mems_allowed(struct task_struct *p) 
	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)

kernel/cpuset.c

+38 −18
Original line number Diff line number Diff line
@@ -581,26 +581,28 @@ static void guarantee_online_cpus(const struct cpuset *cs, cpumask_t *pmask) 


/*

 * 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 @@ static int update_nodemask(struct cpuset *cs, char *buf) 
	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 @@ static int update_nodemask(struct cpuset *cs, char *buf) 
		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 @@ static void guarantee_online_cpus_mems_in_subtree(const struct cpuset *cur) 


/*

 * 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 @@ static void common_cpu_mem_hotplug_unplug(void) 


	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 @@ static int cpuset_handle_cpuhp(struct notifier_block *nb, 


#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 cpuset_track_online_nodes(void) 
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 @@ void cpuset_init_current_mems_allowed(void) 
 *

 * 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.

 **/

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