From owner-freebsd-arch@freebsd.org Sun Feb 14 12:56:29 2016 Return-Path: Delivered-To: freebsd-arch@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 602ADAA0496 for ; Sun, 14 Feb 2016 12:56:29 +0000 (UTC) (envelope-from avi.cohen@huawei.com) Received: from lhrrgout.huawei.com (lhrrgout.huawei.com [194.213.3.17]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "myname.my.domain", Issuer "www.mirapoint.com" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id CF53210C2 for ; Sun, 14 Feb 2016 12:56:28 +0000 (UTC) (envelope-from avi.cohen@huawei.com) Received: from 172.18.7.190 (EHLO lhreml405-hub.china.huawei.com) ([172.18.7.190]) by lhrrg01-dlp.huawei.com (MOS 4.3.7-GA FastPath queued) with ESMTP id CIN47641; Sun, 14 Feb 2016 12:55:17 +0000 (GMT) Received: from LHREML701-CAH.china.huawei.com (10.201.5.93) by lhreml405-hub.china.huawei.com (10.201.5.242) with Microsoft SMTP Server (TLS) id 14.3.235.1; Sun, 14 Feb 2016 12:55:17 +0000 Received: from LHREML501-MBB.china.huawei.com ([10.125.30.98]) by lhreml701-cah.china.huawei.com ([10.201.5.93]) with mapi id 14.03.0235.001; Sun, 14 Feb 2016 12:55:12 +0000 From: Avi Cohen To: "freebsd-arch@freebsd.org" Subject: Paravirtualized KVM clock Thread-Topic: Paravirtualized KVM clock Thread-Index: AdFnJu/nPBQ/VGujSleckJL4Tt9PSQ== Date: Sun, 14 Feb 2016 12:55:11 +0000 Message-ID: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.200.201.159] MIME-Version: 1.0 X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020205.56C07936.003D, ss=1, re=0.000, recu=0.000, reip=0.000, cl=1, cld=1, fgs=0, ip=0.0.0.0, so=2013-06-18 04:22:30, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: bd8bbf2455fda65cd4acb078e7c2b67d Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.20 X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 14 Feb 2016 12:56:29 -0000 Hello My name is Avi Cohen and I work in toganetworks which is part of Huawei ERC= . 1. My VM is Fedora 21 and the host is Fedora 22 (kernels are 4.1 and= 4.2 accordingly) 2. My Intel core processor supports the constant-tsc. 3. The default clock in the guest is kvm-clock . When I run a test to measure packet delay between the host and the VM (wh= ich normally should be about 5 to 10 micro-sec) - I see about 800 mili-s= ec delay I see that delta time between the VM and host is about 800ms - which means= that the sync. Accuracy is bad What accuracy do I have to expect with this clocking mode (kvm-clock) ? te= ns of ms/us/ns? Maybe I've missed some configuration to achieve a better accuracy ? Thanks and Regards, Avi