From owner-freebsd-hackers@FreeBSD.ORG Wed Dec 9 15:16:56 2009 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id E693F1065670 for ; Wed, 9 Dec 2009 15:16:56 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42]) by mx1.freebsd.org (Postfix) with ESMTP id B83268FC14 for ; Wed, 9 Dec 2009 15:16:56 +0000 (UTC) Received: from bigwig.baldwin.cx (66.111.2.69.static.nyinternet.net [66.111.2.69]) by cyrus.watson.org (Postfix) with ESMTPSA id 655CE46B03; Wed, 9 Dec 2009 10:16:56 -0500 (EST) Received: from jhbbsd.localnet (unknown [209.249.190.9]) by bigwig.baldwin.cx (Postfix) with ESMTPA id 589FC8A020; Wed, 9 Dec 2009 10:16:55 -0500 (EST) From: John Baldwin To: freebsd-hackers@freebsd.org Date: Wed, 9 Dec 2009 09:07:33 -0500 User-Agent: KMail/1.12.1 (FreeBSD/7.2-CBSD-20091103; KDE/4.3.1; amd64; ; ) References: <237c27100911260714x2fcb194ew1e6ce11e764efd08@mail.gmail.com> In-Reply-To: <237c27100911260714x2fcb194ew1e6ce11e764efd08@mail.gmail.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200912090907.33433.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.0.1 (bigwig.baldwin.cx); Wed, 09 Dec 2009 10:16:55 -0500 (EST) X-Virus-Scanned: clamav-milter 0.95.1 at bigwig.baldwin.cx X-Virus-Status: Clean X-Spam-Status: No, score=-2.5 required=4.2 tests=AWL,BAYES_00,RDNS_NONE autolearn=no version=3.2.5 X-Spam-Checker-Version: SpamAssassin 3.2.5 (2008-06-10) on bigwig.baldwin.cx Cc: Linda Messerschmidt Subject: Re: Superpages on amd64 FreeBSD 7.2-STABLE X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 09 Dec 2009 15:16:57 -0000 On Thursday 26 November 2009 10:14:20 am Linda Messerschmidt wrote: > It's not clear to me if this might be a problem with the superpages > implementation, or if squid does something particularly horrible to > its memory when it forks to cause this, but I wanted to ask about it > on the list in case somebody who understands it better might know > whats going on. :-) I talked with Alan Cox some about this off-list and there is a case that can cause this behavior if the parent squid process takes write faults on a superpage before the child process has called exec() then it can result in superpages being fragmented and never reassembled. Using vfork() should prevent this from happening. It is a known issue, but it will probably be some time before it is addressed. There is lower hanging fruit in other areas in the VM that will probably be worked on first. -- John Baldwin