From owner-freebsd-bugs@FreeBSD.ORG Thu Mar 20 09:50:00 2014 Return-Path: Delivered-To: freebsd-bugs@smarthost.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id DFB9E7A9 for ; Thu, 20 Mar 2014 09:50:00 +0000 (UTC) Received: from freefall.freebsd.org (freefall.freebsd.org [IPv6:2001:1900:2254:206c::16:87]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id A29B8B92 for ; Thu, 20 Mar 2014 09:50:00 +0000 (UTC) Received: from freefall.freebsd.org (localhost [127.0.0.1]) by freefall.freebsd.org (8.14.8/8.14.8) with ESMTP id s2K9o0h2008167 for ; Thu, 20 Mar 2014 09:50:00 GMT (envelope-from gnats@freefall.freebsd.org) Received: (from gnats@localhost) by freefall.freebsd.org (8.14.8/8.14.8/Submit) id s2K9o0jS008166; Thu, 20 Mar 2014 09:50:00 GMT (envelope-from gnats) Resent-Date: Thu, 20 Mar 2014 09:50:00 GMT Resent-Message-Id: <201403200950.s2K9o0jS008166@freefall.freebsd.org> Resent-From: FreeBSD-gnats-submit@FreeBSD.org (GNATS Filer) Resent-To: freebsd-bugs@FreeBSD.org Resent-Reply-To: FreeBSD-gnats-submit@FreeBSD.org, Alok Kataria Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id D3483777 for ; Thu, 20 Mar 2014 09:47:50 +0000 (UTC) Received: from cgiserv.freebsd.org (cgiserv.freebsd.org [IPv6:2001:1900:2254:206a::50:4]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id BFFFDB76 for ; Thu, 20 Mar 2014 09:47:50 +0000 (UTC) Received: from cgiserv.freebsd.org ([127.0.1.6]) by cgiserv.freebsd.org (8.14.8/8.14.8) with ESMTP id s2K9lo6C036225 for ; Thu, 20 Mar 2014 09:47:50 GMT (envelope-from nobody@cgiserv.freebsd.org) Received: (from nobody@localhost) by cgiserv.freebsd.org (8.14.8/8.14.8/Submit) id s2K9looW036224; Thu, 20 Mar 2014 09:47:50 GMT (envelope-from nobody) Message-Id: <201403200947.s2K9looW036224@cgiserv.freebsd.org> Date: Thu, 20 Mar 2014 09:47:50 GMT From: Alok Kataria To: freebsd-gnats-submit@FreeBSD.org X-Send-Pr-Version: www-3.1 Subject: kern/187783: TSC frequency under virtualization environment is slightly off in overcommitted situations. X-BeenThere: freebsd-bugs@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 20 Mar 2014 09:50:00 -0000 >Number: 187783 >Category: kern >Synopsis: TSC frequency under virtualization environment is slightly off in overcommitted situations. >Confidential: no >Severity: non-critical >Priority: low >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Thu Mar 20 09:50:00 UTC 2014 >Closed-Date: >Last-Modified: >Originator: Alok Kataria >Release: FreeBSD 8.3/8.4 >Organization: VMware >Environment: >Description: We have seen cases where the TSC frequency that kernel calibrates is slightly off from the actual TSC frequency when the FreeBSD kernel is running under a virtualized environment. This problem is amplified when the system is host is overcommitted. We have seen errors as high as 500ppm with the TSC frequency that gets calculated. To solve this problem, FreeBSD 9.x has an updated kernel which instead of calibrating the TSC frequency, queries the hypervisor for that information. It looks like FreeBSD 8.4 will be supported for another year still (June 2015), so to solve this problem I think we should backport that fix for the next 8.4 kernel update too. Since that change has been well tested on 9.x and later it should be pretty low risk IMO. >How-To-Repeat: >Fix: The original fix, which needs to be cross ported can be found here. http://lists.freebsd.org/pipermail/svn-src-head/2011-April/026998.html >Release-Note: >Audit-Trail: >Unformatted: