oom: compare cpuset mems_allowed instead of exclusive ancestors

Instead of testing for overlap in the memory nodes of the the nearest exclusive ancestor of both current and the candidate task, it is better to simply test for intersection between the task's mems_allowed in their task descriptors. This does not require taking callback_mutex since it is only used as a hint in the badness scoring. Tasks that do not have an intersection in their mems_allowed with the current task are not explicitly restricted from being OOM killed because it is quite possible that the candidate task has allocated memory there before and has since changed its mems_allowed. Cc: Andrea Arcangeli <andrea@suse.de> Acked-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

oom: compare cpuset mems_allowed instead of exclusive ancestors
Instead of testing for overlap in the memory nodes of the the nearest exclusive ancestor of both current and the candidate task, it is better to simply test for intersection between the task's mems_allowed in their task descriptors. This does not require taking callback_mutex since it is only used as a hint in the badness scoring. Tasks that do not have an intersection in their mems_allowed with the current task are not explicitly restricted from being OOM killed because it is quite possible that the candidate task has allocated memory there before and has since changed its mems_allowed. Cc: Andrea Arcangeli <andrea@suse.de> Acked-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
David Rientjes · Linus Torvalds
1 parent 7213f5066f
Showing 3 changed files with 16 additions and 35 deletions Side-by-side Diff
include/linux/cpuset.h
kernel/cpuset.c
mm/oom_kill.c
@@ -45,7 +45,8 @@
 		__cpuset_zone_allowed_hardwall(z, gfp_mask);
 }
  
-extern int cpuset_excl_nodes_overlap(const struct task_struct *p);
+extern int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
+					  const struct task_struct *tsk2);
  
 #define cpuset_memory_pressure_bump() 				\
 	do {							\
@@ -113,7 +114,8 @@
 	return 1;
 }
  
-static inline int cpuset_excl_nodes_overlap(const struct task_struct *p)
+static inline int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
+						 const struct task_struct *tsk2)
 {
 	return 1;
 }
@@ -2506,41 +2506,20 @@
 EXPORT_SYMBOL_GPL(cpuset_mem_spread_node);
  
 /**
- * cpuset_excl_nodes_overlap - Do we overlap @p's mem_exclusive ancestors?
- * @p: pointer to task_struct of some other task.
+ * cpuset_mems_allowed_intersects - Does @tsk1's mems_allowed intersect @tsk2's?
+ * @tsk1: pointer to task_struct of some task.
+ * @tsk2: pointer to task_struct of some other task.
  *
- * Description: Return true if the nearest mem_exclusive ancestor
- * cpusets of tasks @p and current overlap.  Used by oom killer to
- * determine if task @p's memory usage might impact the memory
- * available to the current task.
- *
- * Call while holding callback_mutex.
+ * Description: Return true if @tsk1's mems_allowed intersects the
+ * mems_allowed of @tsk2.  Used by the OOM killer to determine if
+ * one of the task's memory usage might impact the memory available
+ * to the other.
  **/
  
-int cpuset_excl_nodes_overlap(const struct task_struct *p)
+int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
+				   const struct task_struct *tsk2)
 {
-	const struct cpuset *cs1, *cs2;	/* my and p's cpuset ancestors */
-	int overlap = 1;		/* do cpusets overlap? */
-
-	task_lock(current);
-	if (current->flags & PF_EXITING) {
-		task_unlock(current);
-		goto done;
-	}
-	cs1 = nearest_exclusive_ancestor(current->cpuset);
-	task_unlock(current);
-
-	task_lock((struct task_struct *)p);
-	if (p->flags & PF_EXITING) {
-		task_unlock((struct task_struct *)p);
-		goto done;
-	}
-	cs2 = nearest_exclusive_ancestor(p->cpuset);
-	task_unlock((struct task_struct *)p);
-
-	overlap = nodes_intersects(cs1->mems_allowed, cs2->mems_allowed);
-done:
-	return overlap;
+	return nodes_intersects(tsk1->mems_allowed, tsk2->mems_allowed);
 }
  
 /*
@@ -143,7 +143,7 @@
 	 * because p may have allocated or otherwise mapped memory on
 	 * this node before. However it will be less likely.
 	 */
-	if (!cpuset_excl_nodes_overlap(p))
+	if (!cpuset_mems_allowed_intersects(current, p))
 		points /= 8;
  
 	/*
...	...	@@ -45,7 +45,8 @@
45	45	__cpuset_zone_allowed_hardwall(z, gfp_mask);
46	46	}
47	47
48		-extern int cpuset_excl_nodes_overlap(const struct task_struct *p);
	48	+extern int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
	49	+ const struct task_struct *tsk2);
49	50
50	51	#define cpuset_memory_pressure_bump() \
51	52	do { \
...	...	@@ -113,7 +114,8 @@
113	114	return 1;
114	115	}
115	116
116		-static inline int cpuset_excl_nodes_overlap(const struct task_struct *p)
	117	+static inline int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
	118	+ const struct task_struct *tsk2)
117	119	{
118	120	return 1;
119	121	}
...	...	@@ -2506,41 +2506,20 @@
2506	2506	EXPORT_SYMBOL_GPL(cpuset_mem_spread_node);
2507	2507
2508	2508	/**
2509		- * cpuset_excl_nodes_overlap - Do we overlap @p's mem_exclusive ancestors?
2510		- * @p: pointer to task_struct of some other task.
	2509	+ * cpuset_mems_allowed_intersects - Does @tsk1's mems_allowed intersect @tsk2's?
	2510	+ * @tsk1: pointer to task_struct of some task.
	2511	+ * @tsk2: pointer to task_struct of some other task.
2511	2512	*
2512		- * Description: Return true if the nearest mem_exclusive ancestor
2513		- * cpusets of tasks @p and current overlap. Used by oom killer to
2514		- * determine if task @p's memory usage might impact the memory
2515		- * available to the current task.
2516		- *
2517		- * Call while holding callback_mutex.
	2513	+ * Description: Return true if @tsk1's mems_allowed intersects the
	2514	+ * mems_allowed of @tsk2. Used by the OOM killer to determine if
	2515	+ * one of the task's memory usage might impact the memory available
	2516	+ * to the other.
2518	2517	**/
2519	2518
2520		-int cpuset_excl_nodes_overlap(const struct task_struct *p)
	2519	+int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
	2520	+ const struct task_struct *tsk2)
2521	2521	{
2522		- const struct cpuset cs1, cs2; /* my and p's cpuset ancestors */
2523		- int overlap = 1; /* do cpusets overlap? */
2524		-
2525		- task_lock(current);
2526		- if (current->flags & PF_EXITING) {
2527		- task_unlock(current);
2528		- goto done;
2529		- }
2530		- cs1 = nearest_exclusive_ancestor(current->cpuset);
2531		- task_unlock(current);
2532		-
2533		- task_lock((struct task_struct *)p);
2534		- if (p->flags & PF_EXITING) {
2535		- task_unlock((struct task_struct *)p);
2536		- goto done;
2537		- }
2538		- cs2 = nearest_exclusive_ancestor(p->cpuset);
2539		- task_unlock((struct task_struct *)p);
2540		-
2541		- overlap = nodes_intersects(cs1->mems_allowed, cs2->mems_allowed);
2542		-done:
2543		- return overlap;
	2522	+ return nodes_intersects(tsk1->mems_allowed, tsk2->mems_allowed);
2544	2523	}
2545	2524
2546	2525	/*
...	...	@@ -143,7 +143,7 @@
143	143	* because p may have allocated or otherwise mapped memory on
144	144	* this node before. However it will be less likely.
145	145	*/
146		- if (!cpuset_excl_nodes_overlap(p))
	146	+ if (!cpuset_mems_allowed_intersects(current, p))
147	147	points /= 8;
148	148
149	149	/*