From owner-freebsd-hackers@FreeBSD.ORG Mon Dec 7 15:20:07 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 17EFE1065670 for ; Mon, 7 Dec 2009 15:20:07 +0000 (UTC) (envelope-from mel.flynn+fbsd.hackers@mailing.thruhere.net) Received: from mailhub.rachie.is-a-geek.net (rachie.is-a-geek.net [66.230.99.27]) by mx1.freebsd.org (Postfix) with ESMTP id CF61D8FC19 for ; Mon, 7 Dec 2009 15:20:06 +0000 (UTC) Received: from smoochies.rachie.is-a-geek.net (mailhub.lan.rachie.is-a-geek.net [192.168.2.11]) by mailhub.rachie.is-a-geek.net (Postfix) with ESMTP id 5F1467E853; Mon, 7 Dec 2009 06:20:05 -0900 (AKST) From: Mel Flynn To: freebsd-hackers@freebsd.org Date: Mon, 7 Dec 2009 16:20:03 +0100 User-Agent: KMail/1.12.1 (FreeBSD/8.0-RC1; KDE/4.3.1; i386; ; ) References: <237c27100911260714x2fcb194ew1e6ce11e764efd08@mail.gmail.com> <867htduvwh.fsf@ds4.des.no> <237c27100911260911w2674b79ds8ac447e900324dce@mail.gmail.com> In-Reply-To: <237c27100911260911w2674b79ds8ac447e900324dce@mail.gmail.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Message-Id: <200912071620.03371.mel.flynn+fbsd.hackers@mailing.thruhere.net> 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: Mon, 07 Dec 2009 15:20:07 -0000 On Thursday 26 November 2009 18:11:10 Linda Messerschmidt wrote: > I did not mean to suggest that we were asking for help solving a > problem with squid rotation. I provided that information as > background to discuss what we observed as a potential misbehavior in > the new VM superpages feature, in the hope that if there is a problem > with the new feature, we can help find/resolve it or, if this is > working as intended, hopefully gain some insight as to what's going > on. I tend to agree with this, though I don't know the nitty gritty of the implementation, it seems that: a) superpages aren't copied efficiently (at all?) on fork and probably other workloads b) vfork is encouraged for memory intensive applications, yet: BUGS This system call will be eliminated when proper system sharing mechanisms are implemented. Users should not depend on the memory sharing semantics of vfork() as it will, in that case, be made synonymous to fork(2). So is this entire problem eliminated when system sharing mechanisms are in place and vfork considered the temporary work around or is copying of superpages a problem that remains? -- Mel