A-Team_Digital_Solutions/android_kernel_motorola_sm6375
Watch
2
0
Fork
You've already forked android_kernel_motorola_sm6375
 0
mirror of https://github.com/BobTheBlinker/android_kernel_motorola_sm6375.git synced 2026-10-28 10:41:38 -04:00
Code Issues Projects Releases Packages Wiki Activity

mm: revert "oom: move oom_adj value"

Browse source 
The commit 2ff05b2b (oom: move oom_adj value) moveed the oom_adj value to
the mm_struct.  It was a very good first step for sanitize OOM.

However Paul Menage reported the commit makes regression to his job
scheduler.  Current OOM logic can kill OOM_DISABLED process.

Why? His program has the code of similar to the following.

	...
	set_oom_adj(OOM_DISABLE); /* The job scheduler never killed by oom */
	...
	if (vfork() == 0) {
		set_oom_adj(0); /* Invoked child can be killed */
		execve("foo-bar-cmd");
	}
	....

vfork() parent and child are shared the same mm_struct.  then above
set_oom_adj(0) doesn't only change oom_adj for vfork() child, it's also
change oom_adj for vfork() parent.  Then, vfork() parent (job scheduler)
lost OOM immune and it was killed.

Actually, fork-setting-exec idiom is very frequently used in userland program.
We must not break this assumption.

Then, this patch revert commit 2ff05b2b and related commit.

Reverted commit list
---------------------
- commit 2ff05b2b4e (oom: move oom_adj value from task_struct to mm_struct)
- commit 4d8b9135c3 (oom: avoid unnecessary mm locking and scanning for OOM_DISABLE)
- commit 8123681022 (oom: only oom kill exiting tasks with attached memory)
- commit 933b787b57 (mm: copy over oom_adj value at fork time)

Signed-off-by: KOSAKI Motohiro <[email protected]>
Cc: Paul Menage <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Nick Piggin <[email protected]>
Cc: Mel Gorman <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
KOSAKI Motohiro 2009-08-18 14:11:10 -07:00 • committed by Linus Torvalds
commit 0753ba01e1
6 changed files with 48 additions and 54 deletions
Download patch file Download diff file Expand all files Collapse all files

15
Documentation/filesystems/proc.txt
View file

@ -1167,13 +1167,11 @@ 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. 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.
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.
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
@ -1187,9 +1185,6 @@ 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: