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authorDavid Rientjes <rientjes@google.com>2009-06-16 15:32:56 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-16 19:47:43 -0700
commit2ff05b2b4eac2e63d345fc731ea151a060247f53 (patch)
tree1840bc2d3b381eca5d39869499339b0fcc6eabbf
parentc9e444103b5e7a5a3519f9913f59767f92e33baf (diff)
downloadlinux-2ff05b2b4eac2e63d345fc731ea151a060247f53.tar.gz
oom: move oom_adj value from task_struct to mm_struct
The per-task oom_adj value is a characteristic of its mm more than the task itself since it's not possible to oom kill any thread that shares the mm. If a task were to be killed while attached to an mm that could not be freed because another thread were set to OOM_DISABLE, it would have needlessly been terminated since there is no potential for future memory freeing. This patch moves oomkilladj (now more appropriately named oom_adj) from struct task_struct to struct mm_struct. This requires task_lock() on a task to check its oom_adj value to protect against exec, but it's already necessary to take the lock when dereferencing the mm to find the total VM size for the badness heuristic. This fixes a livelock if the oom killer chooses a task and another thread sharing the same memory has an oom_adj value of OOM_DISABLE. This occurs because oom_kill_task() repeatedly returns 1 and refuses to kill the chosen task while select_bad_process() will repeatedly choose the same task during the next retry. Taking task_lock() in select_bad_process() to check for OOM_DISABLE and in oom_kill_task() to check for threads sharing the same memory will be removed in the next patch in this series where it will no longer be necessary. Writing to /proc/pid/oom_adj for a kthread will now return -EINVAL since these threads are immune from oom killing already. They simply report an oom_adj value of OOM_DISABLE. Cc: Nick Piggin <npiggin@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mel@csn.ul.ie> 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>
-rw-r--r--Documentation/filesystems/proc.txt15
-rw-r--r--fs/proc/base.c19
-rw-r--r--include/linux/mm_types.h2
-rw-r--r--include/linux/sched.h1
-rw-r--r--mm/oom_kill.c34
5 files changed, 50 insertions, 21 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index cd8717a3627..ebff3c10a07 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -1003,11 +1003,13 @@ CHAPTER 3: PER-PROCESS PARAMETERS
3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score
------------------------------------------------------
-This file can be used to adjust the score used to select which processes
-should be killed in an out-of-memory situation. Giving it a high score will
-increase the likelihood of this process being killed by the oom-killer. Valid
-values are in the range -16 to +15, plus the special value -17, which disables
-oom-killing altogether for this process.
+This file can be used to adjust the score used to select which processes should
+be killed in an out-of-memory situation. The oom_adj value is a characteristic
+of the task's mm, so all threads that share an mm with pid will have the same
+oom_adj value. A high value will increase the likelihood of this process being
+killed by the oom-killer. Valid values are in the range -16 to +15 as
+explained below and a special value of -17, which disables oom-killing
+altogether for threads sharing pid's mm.
The process to be killed in an out-of-memory situation is selected among all others
based on its badness score. This value equals the original memory size of the process
@@ -1021,6 +1023,9 @@ the parent's score if they do not share the same memory. Thus forking servers
are the prime candidates to be killed. Having only one 'hungry' child will make
parent less preferable than the child.
+/proc/<pid>/oom_adj cannot be changed for kthreads since they are immune from
+oom-killing already.
+
/proc/<pid>/oom_score shows process' current badness score.
The following heuristics are then applied:
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 1539e630c47..3ce5ae9e3d2 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1006,7 +1006,12 @@ static ssize_t oom_adjust_read(struct file *file, char __user *buf,
if (!task)
return -ESRCH;
- oom_adjust = task->oomkilladj;
+ task_lock(task);
+ if (task->mm)
+ oom_adjust = task->mm->oom_adj;
+ else
+ oom_adjust = OOM_DISABLE;
+ task_unlock(task);
put_task_struct(task);
len = snprintf(buffer, sizeof(buffer), "%i\n", oom_adjust);
@@ -1035,11 +1040,19 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf,
task = get_proc_task(file->f_path.dentry->d_inode);
if (!task)
return -ESRCH;
- if (oom_adjust < task->oomkilladj && !capable(CAP_SYS_RESOURCE)) {
+ task_lock(task);
+ if (!task->mm) {
+ task_unlock(task);
+ put_task_struct(task);
+ return -EINVAL;
+ }
+ if (oom_adjust < task->mm->oom_adj && !capable(CAP_SYS_RESOURCE)) {
+ task_unlock(task);
put_task_struct(task);
return -EACCES;
}
- task->oomkilladj = oom_adjust;
+ task->mm->oom_adj = oom_adjust;
+ task_unlock(task);
put_task_struct(task);
if (end - buffer == 0)
return -EIO;
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 0e80e26ecf2..f4408106fcb 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -232,6 +232,8 @@ struct mm_struct {
unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */
+ s8 oom_adj; /* OOM kill score adjustment (bit shift) */
+
cpumask_t cpu_vm_mask;
/* Architecture-specific MM context */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1048bf50540..1bc6fae0c13 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1178,7 +1178,6 @@ struct task_struct {
* a short time
*/
unsigned char fpu_counter;
- s8 oomkilladj; /* OOM kill score adjustment (bit shift). */
#ifdef CONFIG_BLK_DEV_IO_TRACE
unsigned int btrace_seq;
#endif
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index a7b2460e922..b60913520ef 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -58,6 +58,7 @@ unsigned long badness(struct task_struct *p, unsigned long uptime)
unsigned long points, cpu_time, run_time;
struct mm_struct *mm;
struct task_struct *child;
+ int oom_adj;
task_lock(p);
mm = p->mm;
@@ -65,6 +66,7 @@ unsigned long badness(struct task_struct *p, unsigned long uptime)
task_unlock(p);
return 0;
}
+ oom_adj = mm->oom_adj;
/*
* The memory size of the process is the basis for the badness.
@@ -148,15 +150,15 @@ unsigned long badness(struct task_struct *p, unsigned long uptime)
points /= 8;
/*
- * Adjust the score by oomkilladj.
+ * Adjust the score by oom_adj.
*/
- if (p->oomkilladj) {
- if (p->oomkilladj > 0) {
+ if (oom_adj) {
+ if (oom_adj > 0) {
if (!points)
points = 1;
- points <<= p->oomkilladj;
+ points <<= oom_adj;
} else
- points >>= -(p->oomkilladj);
+ points >>= -(oom_adj);
}
#ifdef DEBUG
@@ -251,8 +253,12 @@ static struct task_struct *select_bad_process(unsigned long *ppoints,
*ppoints = ULONG_MAX;
}
- if (p->oomkilladj == OOM_DISABLE)
+ task_lock(p);
+ if (p->mm && p->mm->oom_adj == OOM_DISABLE) {
+ task_unlock(p);
continue;
+ }
+ task_unlock(p);
points = badness(p, uptime.tv_sec);
if (points > *ppoints || !chosen) {
@@ -304,8 +310,7 @@ static void dump_tasks(const struct mem_cgroup *mem)
}
printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d %3d %s\n",
p->pid, __task_cred(p)->uid, p->tgid, mm->total_vm,
- get_mm_rss(mm), (int)task_cpu(p), p->oomkilladj,
- p->comm);
+ get_mm_rss(mm), (int)task_cpu(p), mm->oom_adj, p->comm);
task_unlock(p);
} while_each_thread(g, p);
}
@@ -367,8 +372,12 @@ static int oom_kill_task(struct task_struct *p)
* Don't kill the process if any threads are set to OOM_DISABLE
*/
do_each_thread(g, q) {
- if (q->mm == mm && q->oomkilladj == OOM_DISABLE)
+ task_lock(q);
+ if (q->mm == mm && q->mm && q->mm->oom_adj == OOM_DISABLE) {
+ task_unlock(q);
return 1;
+ }
+ task_unlock(q);
} while_each_thread(g, q);
__oom_kill_task(p, 1);
@@ -393,10 +402,11 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
struct task_struct *c;
if (printk_ratelimit()) {
- printk(KERN_WARNING "%s invoked oom-killer: "
- "gfp_mask=0x%x, order=%d, oomkilladj=%d\n",
- current->comm, gfp_mask, order, current->oomkilladj);
task_lock(current);
+ printk(KERN_WARNING "%s invoked oom-killer: "
+ "gfp_mask=0x%x, order=%d, oom_adj=%d\n",
+ current->comm, gfp_mask, order,
+ current->mm ? current->mm->oom_adj : OOM_DISABLE);
cpuset_print_task_mems_allowed(current);
task_unlock(current);
dump_stack();