[PATCH 4/4] cpusets confine oom_killer to mem_exclusive cpuset

Paul Jackson
2005-09-01T09:09:48Z

Now the real motivation for this cpuset mem_exclusive patch series
seems trivial. This patch depends on the previous cpuset_zone_allowed
patch and its prerequisites.

This patch keeps a task in or under one mem_exclusive cpuset from
provoking an oom kill of a task under a non-overlapping mem_exclusive
cpuset. Since only interrupt and GFP_ATOMIC allocations are allowed
to escape mem_exclusive containment, there is little to gain from
oom killing a task under a non-overlapping mem_exclusive cpuset, as
almost all kernel and user memory allocation must come from disjoint
memory nodes.

This patch enables configuring a system so that a runaway job under
one mem_exclusive cpuset cannot cause the killing of a job in another
such cpuset that might be using very high compute and memory resources
for a prolonged time.

Signed-off-by: Paul Jackson <pj@sgi.com>

Index: linux-2.6.13-mem_exclusive_oom/include/linux/cpuset.h
===================================================================
--- linux-2.6.13-mem_exclusive_oom.orig/include/linux/cpuset.h
+++ linux-2.6.13-mem_exclusive_oom/include/linux/cpuset.h
@@ -24,6 +24,7 @@ void cpuset_update_current_mems_allowed(
void cpuset_restrict_to_mems_allowed(unsigned long *nodes);
int cpuset_zonelist_valid_mems_allowed(struct zonelist *zl);
extern int cpuset_zone_allowed(struct zone *z, unsigned int __nocast gfp_mask);
+extern int cpuset_excl_nodes_overlap(const struct task_struct *p);
extern struct file_operations proc_cpuset_operations;
extern char *cpuset_task_status_allowed(struct task_struct *task, char *buffer);

@@ -54,6 +55,11 @@ static inline int cpuset_zone_allowed(st
return 1;
}

+static inline int cpuset_excl_nodes_overlap(const struct task_struct *p)
+{
+ return 1;
+}
+
static inline char *cpuset_task_status_allowed(struct task_struct *task,
char *buffer)
{
Index: linux-2.6.13-mem_exclusive_oom/kernel/cpuset.c
===================================================================
--- linux-2.6.13-mem_exclusive_oom.orig/kernel/cpuset.c
+++ linux-2.6.13-mem_exclusive_oom/kernel/cpuset.c
@@ -1688,6 +1688,39 @@ done:
return allowed;
}

+/**
+ * cpuset_excl_nodes_overlap - Do we overlap @p's mem_exclusive ancestors?
+ * @p: 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.
+ *
+ * Acquires cpuset_sem - not suitable for calling from a fast path.
+ **/
+
+int cpuset_excl_nodes_overlap(const struct task_struct *p)
+{
+ const struct cpuset *cs1, *cs2; /* my and p's cpuset ancestors */
+ int overlap = 0; /* do cpusets overlap? */
+
+ down(&cpuset_sem);
+ cs1 = current->cpuset;
+ if (!cs1)
+ goto done; /* current task exiting */
+ cs2 = p->cpuset;
+ if (!cs2)
+ goto done; /* task p is exiting */
+ cs1 = nearest_exclusive_ancestor(cs1);
+ cs2 = nearest_exclusive_ancestor(cs2);
+ overlap = nodes_intersects(cs1->mems_allowed, cs2->mems_allowed);
+done:
+ up(&cpuset_sem);
+
+ return overlap;
+}
+
/*
* proc_cpuset_show()
* - Print tasks cpuset path into seq_file.
Index: linux-2.6.13-mem_exclusive_oom/mm/oom_kill.c
===================================================================
--- linux-2.6.13-mem_exclusive_oom.orig/mm/oom_kill.c
+++ linux-2.6.13-mem_exclusive_oom/mm/oom_kill.c
@@ -20,6 +20,7 @@
#include <linux/swap.h>
#include <linux/timex.h>
#include <linux/jiffies.h>
+#include <linux/cpuset.h>

/* #define DEBUG */

@@ -152,6 +153,10 @@ static struct task_struct * select_bad_p
continue;
if (p->oomkilladj == OOM_DISABLE)
continue;
+ /* If p's nodes don't overlap ours, it won't help to kill p. */
+ if (!cpuset_excl_nodes_overlap(p))
+ continue;
+
/*
* This is in the process of releasing memory so for wait it
* to finish before killing some other task by mistake.