From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1DQCQW-0001tL-Mm for qemu-devel@nongnu.org; Mon, 25 Apr 2005 18:51:40 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1DQCQU-0001si-4E for qemu-devel@nongnu.org; Mon, 25 Apr 2005 18:51:40 -0400 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1DQCQT-0001oc-UL for qemu-devel@nongnu.org; Mon, 25 Apr 2005 18:51:37 -0400 Received: from [24.71.223.10] (helo=pd2mo3so.prod.shaw.ca) by monty-python.gnu.org with esmtp (Exim 4.34) id 1DQCQL-0001Xx-Hc for qemu-devel@nongnu.org; Mon, 25 Apr 2005 18:51:29 -0400 Received: from pd2mr2so.prod.shaw.ca (pd2mr2so-qfe3.prod.shaw.ca [10.0.141.109]) by l-daemon (Sun ONE Messaging Server 6.0 HotFix 1.01 (built Mar 15 2004)) with ESMTP id <0IFI006Q1XWL0G30@l-daemon> for qemu-devel@nongnu.org; Mon, 25 Apr 2005 16:45:57 -0600 (MDT) Received: from pn2ml5so.prod.shaw.ca ([10.0.121.149]) by pd2mr2so.prod.shaw.ca (Sun ONE Messaging Server 6.0 HotFix 1.01 (built Mar 15 2004)) with ESMTP id <0IFI00EUHXWLKH70@pd2mr2so.prod.shaw.ca> for qemu-devel@nongnu.org; Mon, 25 Apr 2005 16:45:57 -0600 (MDT) Received: from glek.net (S0106000795bd85bd.gv.shawcable.net [24.68.44.127]) by l-daemon (iPlanet Messaging Server 5.2 HotFix 1.18 (built Jul 28 2003)) with ESMTP id <0IFI00J6EXWKAU@l-daemon> for qemu-devel@nongnu.org; Mon, 25 Apr 2005 16:45:57 -0600 (MDT) Received: from [10.1.0.2] (vpn_client [10.1.0.2]) by glek.net (Postfix) with ESMTP id 40FD247F0B3 for ; Mon, 25 Apr 2005 15:45:56 -0700 (PDT) Date: Mon, 25 Apr 2005 15:45:51 -0700 From: Taras Glek Subject: Re: [Qemu-devel] [patch] option -no-tsc for i386 with speedstep In-reply-to: <426D5552.4000104@reactos.com> Message-id: <426D731F.2040701@shaw.ca> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1 Content-transfer-encoding: 7bit References: <20050425111532.GA2554@dizzy.ath.cx> <426D3DBE.9080307@bellard.org> <20050425201706.GA11602@dizzy.ath.cx> <380218305509284f15ded3ac17915cb1@elis.ugent.be> <426D5552.4000104@reactos.com> Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Filip Navara wrote: > Jonas Maebe wrote: > >> On 25 Apr 2005, at 22:17, Massimo Dal Zotto wrote: >> >>> In the meantime until we find a better solution could you give >>> us some explanation on why using a microseconds clock from >>> gettimeofday instead of rdtsc the guest os clock runs always >>> 20% slower? >> >> >> Because a system call (which gettimeofday is) is very slow (two >> context switches). > > > I remember there was a Linux patch which changed the gettimeofday > function to read the info from user mode shared page (which is > updated by the kernel) and thus avoided the syscall overhead. Not > sure if/when it was integrated into the official sources... > > (Once again Windows NT were ahead of time with this idea > implemented way earlier ;-) Another *solution* is to use kernel mode linux =). See http://web.yl.is.s.u-tokyo.ac.jp/~tosh/kml/ It makes already low Linux syscall overhead much lower. Tara -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.0 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFCbXMfmzwUPloTW30RAg+7AKCh0jGnYhvRp0/qtwm36wXDrCxd2ACgpdMi LBQsxo56m98yPvkAPFJ0PAQ= =jpKR -----END PGP SIGNATURE-----