linux-kernel - Re: [PATCH v3] oom-kill: add lowmem usage aware oom kill handling

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Message-Id: <20100127085355.f5306e78.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Wed, 27 Jan 2010 08:53:55 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>, rientjes@...gle.com,
	minchan.kim@...il.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>
Subject: Re: [PATCH v3] oom-kill: add lowmem usage aware oom kill handling

On Tue, 26 Jan 2010 15:12:02 -0800
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Mon, 25 Jan 2010 15:15:03 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:

> > This patch does
> >   - add sysctl for new bahavior.
> >   - add CONSTRAINT_LOWMEM to oom's constraint type.
> >   - pass constraint to __badness()
> >   - change calculation based on constraint. If CONSTRAINT_LOWMEM,
> >     use low_rss instead of vmsize.
> > 
> > Changelog 2010/01/25
> >  - showing extension_mask value in OOM kill main log header.
> > Changelog 2010/01/22:
> >  - added sysctl
> >  - fixed !CONFIG_MMU
> >  - fixed fs/proc/base.c breakacge.
> 
> It'd be nice to see some testing results for this.  Perhaps "here's a
> test case and here's the before-and-after behaviour".
> 
Hm. posting test case module is O.K ?
At leaset, I'll add what test was done and /var/log/message output to the log.


> I don't like the sysctl knob much. 
me, too.

> Hardly anyone will know to enable
> it so the feature won't get much testing and this binary decision
> fractures the testing effort.  It would be much better if we can get
> everyone running the same code.  I mean, if there are certain workloads
> on certain machines with which the oom-killer doesn't behave correctly
> then fix it!
Yes, I think you're right. But "breaking current behaviro of our servers!"
arguments kills all proposal to this area and this oom-killer or vmscan is
a feature should be tested by real users. (I'll write fork-bomb detector
and RSS based OOM again.)

Then, I'd like to use sysctl. Distro/users can select default value of this
by /etc/sysctl.conf file, at least.


> 
> Why was the '#include <linux/sysctl.h>" removed from sysctl.c?
> 
> The patch adds a random newline to sysctl.c.
> 
Sorry. my bad.


> It was never a good idea to add extern declarations to sysctl.c.  It's
> better to add them to a subsystem-specific header file (ie:
> mm-sysctl.h) and then include that file from the mm files that define
> or use sysctl_foo, and include it into sysctl.c.  Oh well.
> 
Hmm. Okay. I'll consider about that.

Thanks,
-Kame

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