From owner-freebsd-xen@FreeBSD.ORG Sat Mar 20 16:22:23 2010 Return-Path: Delivered-To: freebsd-xen@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 01F92106564A for ; Sat, 20 Mar 2010 16:22:23 +0000 (UTC) (envelope-from bms@incunabulum.net) Received: from out2.smtp.messagingengine.com (out2.smtp.messagingengine.com [66.111.4.26]) by mx1.freebsd.org (Postfix) with ESMTP id C32288FC0A for ; Sat, 20 Mar 2010 16:22:22 +0000 (UTC) Received: from compute1.internal (compute1.internal [10.202.2.41]) by gateway1.messagingengine.com (Postfix) with ESMTP id 3FBC2E75E3 for ; Sat, 20 Mar 2010 12:22:22 -0400 (EDT) Received: from heartbeat1.messagingengine.com ([10.202.2.160]) by compute1.internal (MEProxy); Sat, 20 Mar 2010 12:22:22 -0400 DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d=messagingengine.com; h=message-id:date:from:mime-version:to:subject:references:in-reply-to:content-type:content-transfer-encoding; s=smtpout; bh=zpicYzdvRKUy4G84MUWbONdlX38=; b=l9AAHUwHcuvAPWfruHoK2yKWzljKKcA9F0nn3XDHZZYctIS3X8zMG4eQ/d08fhsznlUMgWdt3TgjmqMRCBXMcfY3K1b3u+f+ZT/H/tkm15nrCpXXfwuxSQrrEy+TR6/FHa1sWfzxcT2ugvjtoff3zKvjFhKMN6AVqeJqA/qACBc= X-Sasl-enc: qM2ZYZRWs6nWqr4qeQpIpiGUIb5tdg0OHLbRZIGuO1WR 1269102142 Received: from anglepoise.lon.incunabulum.net (cpc2-dals7-0-0-cust253.hari.cable.virginmedia.com [82.35.112.254]) by mail.messagingengine.com (Postfix) with ESMTPSA id DF44A4D0487 for ; Sat, 20 Mar 2010 12:22:21 -0400 (EDT) Message-ID: <4BA4F63C.1070407@incunabulum.net> Date: Sat, 20 Mar 2010 16:22:20 +0000 From: Bruce Simpson User-Agent: Mozilla/5.0 (X11; U; FreeBSD amd64; en-US; rv:1.9.1.8) Gecko/20100302 Thunderbird/3.0.3 MIME-Version: 1.0 To: freebsd-xen@freebsd.org References: <20100318204746.GA57903@cons.org> <4BA4F5A6.508@incunabulum.net> In-Reply-To: <4BA4F5A6.508@incunabulum.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: FreeBSD on Xen with hw virtualization support X-BeenThere: freebsd-xen@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion of the freebsd port to xen - implementation and usage List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 20 Mar 2010 16:22:23 -0000 On 03/20/10 16:19, Bruce Simpson wrote: > > There is a performance penalty, because Xen has to emulate real > hardware for HVM, using code largely cribbed from QEMU. > > Normally this happens within the hypervisor itself, however, this is > problematic, because there is then no good way to book the > CPU/memory/IO involved to the domU doing the I/O. This in turn affects > scheduling parameters. Correction: mostly dom0 with some hypervisor bits on top. But this still screws up HVM domU accounting. In a hosting environment, this is all important. Chisnall's Xen book explains this in great detail.