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
-------------------------------------------------------