linux-kernel - Re: [RFC][PATCH] VM: per-user overcommit policy

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Message-ID: <20070508125411.07de2340@the-village.bc.nu>
Date:	Tue, 8 May 2007 12:54:11 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	righiandr@...rs.sourceforge.net
Cc:	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: [RFC][PATCH] VM: per-user overcommit policy

> When $VERY_CRITICAL_DAEMON dies *all* the users blame the sysadmin [me]. If a
> user application dies because a malloc() returns NULL, the sysadmin [I] can
> blame the user saying: "hey! _you_ tried to hog the machine and _your_
> application is not able to handle the NULL result of the malloc()s!"... :-)

If you allow overcommit by the daemons and not user space then some of
the time you will still get out of memory kills which may well hit your
daemon process.

> A solution could be to define the critical processes unkillable via
> /proc/<pid>/oom_adj, but the per-process approach doesn't resolve all the
> possible cases and it's quite difficult to manage in big environments, like HPC
> clusters.

If you are running no overcommit you should never get an out of memory
kill.

> Anyway, it seems that I need to deepen my knowledge about the recent development
> of process containers and openvz...

I think that does what you need - you'd create containers for critical
services and for the users and split resources to protect one from the
other.
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