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Date:	Sat, 30 Jan 2010 18:30:38 +0100
From:	Vedran Fura─Ź <>
To:	Alan Cox <>
CC:	KAMEZAWA Hiroyuki <>,
	Andrew Morton <>,
	"" <>,,,
	"" <>,
	"" <>
Subject: Re: [PATCH v3] oom-kill: add lowmem usage aware oom kill handling

Alan Cox wrote:

>>> So how about you go and have a complain at the people who are causing
>>> your problem, rather than the kernel.
>> That would pass completely unnoticed and ignored as long as overcommit
>> is enabled by default.
> Defaults are set by the distributions. So you are still complaining to
> the wrong people.

I can't say I'm able to correctly read kernel code, but I believe
default is set by:

int sysctl_overcommit_memory = OVERCOMMIT_GUESS;  /* heuristic overcommit */
int sysctl_overcommit_ratio = 50;       /* default is 50% */
int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;

in mmap.c.

>> So, if you don't want to change the OOM algorithm why not fixing this
>> bug then? And after that change the proc(5) manpage entry for
>> /proc/sys/vm/overcommit_memory into something like:
>> 0: heuristic overcommit (enable this if you have memory problems with
>>                           some buggy software)
>> 1: always overcommit, never check
>> 2: always check, never overcommit (this is the default)
> Because there are a lot of systems where heuristic overcommit makes
> sense ?

Ok, I won't argue any more. Just please watch this short (~1min)
screencast I made and tell me which behavior is good and which is bad
and should be fixed:  (you can watch it using VLC for example)

Actually anyone receiving this mail should see it. What do you think,
what will customers rather choose if they see this?


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