mm, oom: reintroduce /proc/pid/oom_adj
This is mostly a revert of 01dc52ebdf47 ("oom: remove deprecated oom_adj")
from Davidlohr Bueso.
It reintroduces /proc/pid/oom_adj for backwards compatibility with earlier
kernels. It simply scales the value linearly when /proc/pid/oom_score_adj
is written.
The major difference is that its scheduled removal is no longer included
in Documentation/feature-removal-schedule.txt. We do warn users with a
single printk, though, to suggest the more powerful and supported
/proc/pid/oom_score_adj interface.
Reported-by: Artem S. Tashkinov <t.artem@lycos.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index a1793d6..3844d21 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -33,7 +33,7 @@
2 Modifying System Parameters
3 Per-Process Parameters
- 3.1 /proc/<pid>/oom_score_adj - Adjust the oom-killer
+ 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer
score
3.2 /proc/<pid>/oom_score - Display current oom-killer score
3.3 /proc/<pid>/io - Display the IO accounting fields
@@ -1320,10 +1320,10 @@
CHAPTER 3: PER-PROCESS PARAMETERS
------------------------------------------------------------------------------
-3.1 /proc/<pid>/oom_score_adj- Adjust the oom-killer score
+3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
--------------------------------------------------------------------------------
-This file can be used to adjust the badness heuristic used to select which
+These file can be used to adjust the badness heuristic used to select which
process gets killed in out of memory conditions.
The badness heuristic assigns a value to each candidate task ranging from 0
@@ -1361,6 +1361,12 @@
equivalent to discounting 50% of the task's allowed memory from being considered
as scoring against the task.
+For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
+be used to tune the badness score. Its acceptable values range from -16
+(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
+(OOM_DISABLE) to disable oom killing entirely for that task. Its value is
+scaled linearly with /proc/<pid>/oom_score_adj.
+
The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
requires CAP_SYS_RESOURCE.
@@ -1375,7 +1381,9 @@
-------------------------------------------------------------
This file can be used to check the current score used by the oom-killer is for
-any given <pid>.
+any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
+process should be killed in an out-of-memory situation.
+
3.3 /proc/<pid>/io - Display the IO accounting fields
-------------------------------------------------------
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 144a967..3c231ad 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -873,6 +873,113 @@
.release = mem_release,
};
+static ssize_t oom_adj_read(struct file *file, char __user *buf, size_t count,
+ loff_t *ppos)
+{
+ struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
+ char buffer[PROC_NUMBUF];
+ int oom_adj = OOM_ADJUST_MIN;
+ size_t len;
+ unsigned long flags;
+
+ if (!task)
+ return -ESRCH;
+ if (lock_task_sighand(task, &flags)) {
+ if (task->signal->oom_score_adj == OOM_SCORE_ADJ_MAX)
+ oom_adj = OOM_ADJUST_MAX;
+ else
+ oom_adj = (task->signal->oom_score_adj * -OOM_DISABLE) /
+ OOM_SCORE_ADJ_MAX;
+ unlock_task_sighand(task, &flags);
+ }
+ put_task_struct(task);
+ len = snprintf(buffer, sizeof(buffer), "%d\n", oom_adj);
+ return simple_read_from_buffer(buf, count, ppos, buffer, len);
+}
+
+static ssize_t oom_adj_write(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ struct task_struct *task;
+ char buffer[PROC_NUMBUF];
+ int oom_adj;
+ unsigned long flags;
+ int err;
+
+ memset(buffer, 0, sizeof(buffer));
+ if (count > sizeof(buffer) - 1)
+ count = sizeof(buffer) - 1;
+ if (copy_from_user(buffer, buf, count)) {
+ err = -EFAULT;
+ goto out;
+ }
+
+ err = kstrtoint(strstrip(buffer), 0, &oom_adj);
+ if (err)
+ goto out;
+ if ((oom_adj < OOM_ADJUST_MIN || oom_adj > OOM_ADJUST_MAX) &&
+ oom_adj != OOM_DISABLE) {
+ err = -EINVAL;
+ goto out;
+ }
+
+ task = get_proc_task(file->f_path.dentry->d_inode);
+ if (!task) {
+ err = -ESRCH;
+ goto out;
+ }
+
+ task_lock(task);
+ if (!task->mm) {
+ err = -EINVAL;
+ goto err_task_lock;
+ }
+
+ if (!lock_task_sighand(task, &flags)) {
+ err = -ESRCH;
+ goto err_task_lock;
+ }
+
+ /*
+ * Scale /proc/pid/oom_score_adj appropriately ensuring that a maximum
+ * value is always attainable.
+ */
+ if (oom_adj == OOM_ADJUST_MAX)
+ oom_adj = OOM_SCORE_ADJ_MAX;
+ else
+ oom_adj = (oom_adj * OOM_SCORE_ADJ_MAX) / -OOM_DISABLE;
+
+ if (oom_adj < task->signal->oom_score_adj &&
+ !capable(CAP_SYS_RESOURCE)) {
+ err = -EACCES;
+ goto err_sighand;
+ }
+
+ /*
+ * /proc/pid/oom_adj is provided for legacy purposes, ask users to use
+ * /proc/pid/oom_score_adj instead.
+ */
+ printk_once(KERN_WARNING "%s (%d): /proc/%d/oom_adj is deprecated, please use /proc/%d/oom_score_adj instead.\n",
+ current->comm, task_pid_nr(current), task_pid_nr(task),
+ task_pid_nr(task));
+
+ task->signal->oom_score_adj = oom_adj;
+ trace_oom_score_adj_update(task);
+err_sighand:
+ unlock_task_sighand(task, &flags);
+err_task_lock:
+ task_unlock(task);
+ put_task_struct(task);
+out:
+ return err < 0 ? err : count;
+}
+
+static const struct file_operations proc_oom_adj_operations = {
+ .read = oom_adj_read,
+ .write = oom_adj_write,
+ .llseek = generic_file_llseek,
+};
+
static ssize_t oom_score_adj_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
@@ -2598,6 +2705,7 @@
REG("cgroup", S_IRUGO, proc_cgroup_operations),
#endif
INF("oom_score", S_IRUGO, proc_oom_score),
+ REG("oom_adj", S_IRUGO|S_IWUSR, proc_oom_adj_operations),
REG("oom_score_adj", S_IRUGO|S_IWUSR, proc_oom_score_adj_operations),
#ifdef CONFIG_AUDITSYSCALL
REG("loginuid", S_IWUSR|S_IRUGO, proc_loginuid_operations),
@@ -2964,6 +3072,7 @@
REG("cgroup", S_IRUGO, proc_cgroup_operations),
#endif
INF("oom_score", S_IRUGO, proc_oom_score),
+ REG("oom_adj", S_IRUGO|S_IWUSR, proc_oom_adj_operations),
REG("oom_score_adj", S_IRUGO|S_IWUSR, proc_oom_score_adj_operations),
#ifdef CONFIG_AUDITSYSCALL
REG("loginuid", S_IWUSR|S_IRUGO, proc_loginuid_operations),
diff --git a/include/uapi/linux/oom.h b/include/uapi/linux/oom.h
index a49c4af..b29272d 100644
--- a/include/uapi/linux/oom.h
+++ b/include/uapi/linux/oom.h
@@ -8,4 +8,13 @@
#define OOM_SCORE_ADJ_MIN (-1000)
#define OOM_SCORE_ADJ_MAX 1000
+/*
+ * /proc/<pid>/oom_adj set to -17 protects from the oom killer for legacy
+ * purposes.
+ */
+#define OOM_DISABLE (-17)
+/* inclusive */
+#define OOM_ADJUST_MIN (-16)
+#define OOM_ADJUST_MAX 15
+
#endif /* _UAPI__INCLUDE_LINUX_OOM_H */