From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Ky5n2-0000IU-21 for qemu-devel@nongnu.org; Thu, 06 Nov 2008 09:24:52 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1Ky5n0-0000Hn-5X for qemu-devel@nongnu.org; Thu, 06 Nov 2008 09:24:51 -0500 Received: from [199.232.76.173] (port=46545 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Ky5n0-0000Hk-3H for qemu-devel@nongnu.org; Thu, 06 Nov 2008 09:24:50 -0500 Received: from mail.codesourcery.com ([65.74.133.4]:34000) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1Ky5mx-0001hU-Qg for qemu-devel@nongnu.org; Thu, 06 Nov 2008 09:24:48 -0500 From: Paul Brook Subject: Re: [Qemu-devel] [RESEND][PATCH 0/3] Fix guest time drift under heavy load. Date: Thu, 6 Nov 2008 15:24:42 +0100 References: <20081029152236.14831.15193.stgit@dhcp-1-237.local> <20081106081206.GD3820@redhat.com> <4912FAE5.9010100@codemonkey.ws> In-Reply-To: <4912FAE5.9010100@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset="windows-1255" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200811061424.43689.paul@codesourcery.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 Cc: Gleb Natapov > You see time drift with 100hz timers in the guest?? That makes very > little sense as even without hr timers, the host should have no problem > delivering a 10ms timer. If your host has HZ=100 and no HR timers than a 10ms interval is fairly borderline, and it's not that hard to end up missing an interrupt, especially under heavy load. If part of qemu gets swapped out then all bets are off, and you can easily stall for significant fractions of a second. No amount of host high resolution time support will help you there. Paul