Re: [PATCH] oom_kill: use rss value instead of vm size for badness

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

> I'll wait until the next week to post a new patch.
> We don't need rapid way.
> 
I wrote above...but for my mental health, this is bug-fixed version.
Sorry for my carelessness. David, thank you for your review.
Regards,
-Kame
==
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

It's reported that OOM-Killer kills Gnone/KDE at first...
And yes, we can reproduce it easily.

Now, oom-killer uses mm->total_vm as its base value. But in recent
applications, there are a big gap between VM size and RSS size.
Because
  - Applications attaches much dynamic libraries. (Gnome, KDE, etc...)
  - Applications may alloc big VM area but use small part of them.
    (Java, and multi-threaded applications has this tendency because
     of default-size of stack.)

I think using mm->total_vm as score for oom-kill is not good.
By the same reason, overcommit memory can't work as expected.
(In other words, if we depends on total_vm, using overcommit more positive
 is a good choice.)

This patch uses mm->anon_rss/file_rss as base value for calculating badness.

Following is changes to OOM score(badness) on an environment with 1.6G memory
plus memory-eater(500M & 1G).

Top 10 of badness score. (The highest one is the first candidate to be killed)
Before
badness program
91228	gnome-settings-
94210	clock-applet
103202	mixer_applet2
106563	tomboy
112947	gnome-terminal
128944	mmap              <----------- 500M malloc
129332	nautilus
215476	bash              <----------- parent of 2 mallocs.
256944	mmap              <----------- 1G malloc
423586	gnome-session

After
badness 
1911	mixer_applet2
1955	clock-applet
1986	xinit
1989	gnome-session
2293	nautilus
2955	gnome-terminal
4113	tomboy
104163	mmap             <----------- 500M malloc.
168577	bash             <----------- parent of 2 mallocs
232375	mmap             <----------- 1G malloc

seems good for me. Maybe we can tweak this patch more,
but this one will be a good one as a start point.

Changelog: 2009/10/29
 - use get_mm_rss() instead of get_mm_counter()

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 mm/oom_kill.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: mm-test-kernel/mm/oom_kill.c
===================================================================
--- mm-test-kernel.orig/mm/oom_kill.c
+++ mm-test-kernel/mm/oom_kill.c
@@ -93,7 +93,7 @@ unsigned long badness(struct task_struct
 	/*
 	 * The memory size of the process is the basis for the badness.
 	 */
-	points = mm->total_vm;
+	points = get_mm_rss(mm);
 
 	/*
 	 * After this unlock we can no longer dereference local variable `mm'
@@ -117,7 +117,7 @@ unsigned long badness(struct task_struct
 	list_for_each_entry(child, &p->children, sibling) {
 		task_lock(child);
 		if (child->mm != mm && child->mm)
-			points += child->mm->total_vm/2 + 1;
+			points += get_mm_rss(child->mm)/2 + 1;
 		task_unlock(child);
 	}
 


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