Re: Memory overcommit

From: David Rientjes
Date: Tue Nov 03 2009 - 15:50:07 EST

On Fri, 30 Oct 2009, KAMEZAWA Hiroyuki wrote:

> > > - The kernel can't know the program is bad or not. just guess it.
> >
> > Totally irrelevant, given your fourth point about /proc/pid/oom_adj. We
> > can tell the kernel what we'd like the oom killer behavior should be if
> > the situation arises.
> >
> My point is that the server cannot distinguish memory leak from intentional
> memory usage. No other than that.

That's a different point. Today, we can influence the badness score of
any user thread to prioritize oom killing from userspace and that can be
done regardless of whether there's a memory leaker, a fork bomber, etc.
The priority based oom killing is important to production scenarios and
cannot be replaced by a heuristic that works everytime if it cannot be
influenced by userspace.

A spike in memory consumption when a process is initially forked would be
defined as a memory leaker in your quiet_time model.

> In this summer, at lunch with a daily linux user, I was said
> "you, enterprise guys, don't consider desktop or laptop problem at all."
> yes, I use only servers. My customer uses server, too. My first priority
> is always on server users.
> But, for this time, I wrote reply to Vedran and try to fix desktop problem.
> Even if current logic works well for servers, "KDE/GNOME is killed" problem
> seems to be serious. And this may be a problem for EMBEDED people, I guess.

You argued before that the problem wasn't specific to X (after I said you
could protect it very trivially with /proc/pid/oom_adj set to
OOM_DISABLE), but that's now your reasoning for rewriting the oom killer

> I can say the same thing to total_vm size. total_vm size doesn't include any
> good information for oom situation. And tweaking based on that not-useful
> parameter will make things worse.

Tweaking on the heuristic will probably make it more convoluted and
overall worse, I agree. But it's a more stable baseline than rss from
which we can set oom killing priorities from userspace.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at