From owner-freebsd-stable@FreeBSD.ORG  Tue Sep 28 16:24:48 2010
Return-Path: <owner-freebsd-stable@FreeBSD.ORG>
Delivered-To: stable@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id A33D21065674;
	Tue, 28 Sep 2010 16:24:48 +0000 (UTC)
	(envelope-from ben@wanderview.com)
Received: from mail.wanderview.com (mail.wanderview.com [66.92.166.102])
	by mx1.freebsd.org (Postfix) with ESMTP id 297328FC1B;
	Tue, 28 Sep 2010 16:24:47 +0000 (UTC)
Received: from xykon.in.wanderview.com (xykon.in.wanderview.com [10.76.10.152])
	(authenticated bits=0)
	by mail.wanderview.com (8.14.4/8.14.4) with ESMTP id o8SFo5c9027002
	(version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NO);
	Tue, 28 Sep 2010 15:50:06 GMT (envelope-from ben@wanderview.com)
Mime-Version: 1.0 (Apple Message framework v1081)
Content-Type: text/plain; charset=us-ascii
From: Ben Kelly <ben@wanderview.com>
In-Reply-To: <4CA1EF69.4040402@icyb.net.ua>
Date: Tue, 28 Sep 2010 11:50:05 -0400
Content-Transfer-Encoding: quoted-printable
Message-Id: <FE116FEC-714D-4BF5-86D8-E29BFA713C69@wanderview.com>
References: <4CA1D06C.9050305@digiware.nl>
	<20100928115047.GA62142__15392.0458550148$1285675457$gmane$org@icarus.home.lan>
	<4CA1DDE9.8090107@icyb.net.ua>
	<20100928132355.GA63149@icarus.home.lan>
	<4CA1EF69.4040402@icyb.net.ua>
To: Andriy Gapon <avg@icyb.net.ua>
X-Mailer: Apple Mail (2.1081)
X-Spam-Score: -1.01 () ALL_TRUSTED,T_RP_MATCHES_RCVD
X-Scanned-By: MIMEDefang 2.67 on 10.76.20.1
Cc: stable@freebsd.org, Willem Jan Withagen <wjw@digiware.nl>, fs@freebsd.org,
	Jeremy Chadwick <freebsd@jdc.parodius.com>
Subject: Re: Still getting kmem exhausted panic
X-BeenThere: freebsd-stable@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Production branch of FreeBSD source code <freebsd-stable.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-stable>, 
	<mailto:freebsd-stable-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-stable>
List-Post: <mailto:freebsd-stable@freebsd.org>
List-Help: <mailto:freebsd-stable-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-stable>,
	<mailto:freebsd-stable-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 28 Sep 2010 16:24:48 -0000


On Sep 28, 2010, at 9:36 AM, Andriy Gapon wrote:
> Well, no time for me to dig through all that history.
> arc_max should be a hard limit and it is now. If it ever wasn't then =
it was a bug.

I believe the size of the arc could exceed the limit if your working set =
was larger than arc_max.  The arc can't (couldn't then, anyway) evict =
data that is still referenced.

A contributing factor at the time was that the page daemon did not take =
into account back pressure from the arc when deciding which pages to =
move from active to inactive, etc.  So data was more likely to be =
referenced and therefore forced to remain in the arc.

I'm not sure if this is still the current state.  I seem to remember =
some changesets mentioning arc back pressure at some point, but I don't =
know the details.

- Ben=