From owner-svn-src-all@FreeBSD.ORG Tue Nov 15 21:45:15 2011 Return-Path: Delivered-To: svn-src-all@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 4F13B1065672; Tue, 15 Nov 2011 21:45:15 +0000 (UTC) (envelope-from yanegomi@gmail.com) Received: from mail-yw0-f54.google.com (mail-yw0-f54.google.com [209.85.213.54]) by mx1.freebsd.org (Postfix) with ESMTP id D31D68FC14; Tue, 15 Nov 2011 21:45:14 +0000 (UTC) Received: by ywe9 with SMTP id 9so6096705ywe.13 for ; Tue, 15 Nov 2011 13:45:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=subject:mime-version:content-type:from:in-reply-to:date:cc :message-id:references:to:x-mailer; bh=QXV7CetnLR9QTAQnSTXrWuoMFKmi3qIbeXWi3XJ84DQ=; b=gCbiwHYt85NyUT0JkygNRmxFnaTxHhMGZzCTIWOW9FfaPnyRU2aihziVMcKZliRVOs sLURgg53na3bu0SOboH0o6rzaA2tOblR3Bpz1L4Zrshdmb1gfXEqZ/F6ZQ3JHYftyudK aEbTR79OW5JFbv/wMDSSefwYjN9ZGYd9aAenY= Received: by 10.68.21.202 with SMTP id x10mr45161476pbe.128.1321393513429; Tue, 15 Nov 2011 13:45:13 -0800 (PST) Received: from kruse-180.4.ixsystems.com (drawbridge.ixsystems.com. [206.40.55.65]) by mx.google.com with ESMTPS id w8sm4381880pbw.18.2011.11.15.13.45.11 (version=TLSv1/SSLv3 cipher=OTHER); Tue, 15 Nov 2011 13:45:12 -0800 (PST) Mime-Version: 1.0 (Apple Message framework v1084) From: Garrett Cooper In-Reply-To: <201111152224.27868.hselasky@c2i.net> Date: Tue, 15 Nov 2011 13:45:10 -0800 Message-Id: <1A1FDBC6-90A1-4C4A-B2C6-62B40FD2B523@gmail.com> References: <201111152048.pAFKmvNC016452@svn.freebsd.org> <201111152224.27868.hselasky@c2i.net> To: Hans Petter Selasky X-Mailer: Apple Mail (2.1084) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: "svn-src-head@freebsd.org" , mdf@freebsd.org, "svn-src-all@freebsd.org" , "src-committers@freebsd.org" Subject: Re: svn commit: r227541 - head/sys/dev/usb/controller X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 15 Nov 2011 21:45:15 -0000 On Nov 15, 2011, at 1:24 PM, Hans Petter Selasky wrote: >>=20 >> ... and I also just remembered that I have seen recommendations that, >> when FreeBSD is used as a virtual machine, hz should be set to 100 so >> that the virtual interrupt overhead is reduced. Those two >> recommendations are at odds with each other. >=20 > USB in virtual machines is a completely different story. All the = timing=20 > critical stuff is handled by the real USB host operating system. The = OS inside=20 > the VM just has to respond to some "virtual" USB events. Timing does = not=20 kern.hz=3D100 (!=3D 1000) recommendation matters because: 1. It causes too many interrupts on multicore systems, which folks = reported caused performance degradation. 2. In VMs it caused clock skew IIRC. I could dig up sources if you need them. Thanks, -Garrett=