Re: oom killer in 2.4.23

From: Andrea Arcangeli <andrea@suse.de>
To: Kristian Peters <kristian.peters@korseby.net>
Cc: lkml <linux-kernel@vger.kernel.org>
Subject: Re: oom killer in 2.4.23
Date: Fri, 5 Dec 2003 20:58:00 +0100	[thread overview]
Message-ID: <20031205195800.GB2121@dualathlon.random> (raw)
In-Reply-To: <20031205140520.39289a3a.kristian.peters@korseby.net>

On Fri, Dec 05, 2003 at 02:05:20PM +0100, Kristian Peters wrote:
> Andrea Arcangeli <andrea@suse.de> schrieb:
> > Marcelo asked me to to make it configurable at runtime so you could go
> > in the deadlock prone stautus of 2.4.22 on demand, but I'm not going to
> > add more features to 2.4 today unless they're blocker bugs (even if that
> > would be simple to implement), actually it's not even my choice so don't
> > ask me for that sorry.
> 
> Andrea, your vm does not work correctly in any cases.

what you're complaining is the 'selection of the task to be killed'.
That's not solvable. the kernel can't read your brain period. Only if
the kernel could read the brain of the adminstrator then you would be
happy, there is no way the kernel can know which is the task you really
want to have killed first.

> It's so simple. I've tried to fill up my memory with that crappy
> khexedit that comes with kde2. You'll see how my memory fills with the
> contents of the whole file I load. When I have started 2 or 3
> instances of khexedit my memory was nearly completely filled. Than I
> tried to start another khexedit (with a file that should nearly fit
> into memory), and the pain began.

The kernel can't know what is a pain for you and what is pain for other
people.

Measuring the page fault rate seems to get the closest heuristic that
may not be a pain for most people, all current oom killers are a pain
for somebody, desktop users where pretty much fine with 2.4.22, server
users had pain with 2.4.22 and should have less pain with 2.4.23. There
is no way to make everybody happy in 2.4.

> Rick's old vm worked better. It'd have killed the task that had last allocated memory.

it was the biggest one that's why. the old omm killer gets your desktop
scenario always correctly, true, (as far as your biggest task doesn't
get stuck on nfs etc..)

> PS: If you need more details it should be no problem to do this again.

I'm aware about those issues, that's a feature not a bug.