From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LhNwr-0007HP-Ue for qemu-devel@nongnu.org; Wed, 11 Mar 2009 08:54:13 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LhNwr-0007HB-57 for qemu-devel@nongnu.org; Wed, 11 Mar 2009 08:54:13 -0400 Received: from [199.232.76.173] (port=44303 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LhNwq-0007Gl-T0 for qemu-devel@nongnu.org; Wed, 11 Mar 2009 08:54:12 -0400 Received: from main.gmane.org ([80.91.229.2]:46822 helo=ciao.gmane.org) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1LhNwq-0000mA-9U for qemu-devel@nongnu.org; Wed, 11 Mar 2009 08:54:12 -0400 Received: from list by ciao.gmane.org with local (Exim 4.43) id 1LhNwn-0007h6-HU for qemu-devel@nongnu.org; Wed, 11 Mar 2009 12:54:10 +0000 Received: from 141.76.6.219 ([141.76.6.219]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 11 Mar 2009 12:54:09 +0000 Received: from usenet by 141.76.6.219 with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 11 Mar 2009 12:54:09 +0000 From: Steffen Liebergeld Date: Wed, 11 Mar 2009 12:53:53 +0000 (UTC) Message-ID: References: <761ea48b0903091456r319a017dlda891b6eca800520@mail.gmail.com> <761ea48b0903110342i3317f650hd00302ca47bf9843@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: news Subject: [Qemu-devel] Re: Precise guest instruction count. 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 Hi, Laurent Desnogues schrieb: > On Wed, Mar 11, 2009 at 11:33 AM, Steffen Liebergeld wrote: >> I temporarily disabled timers in Qemu, so normally time should not >> influence my measurements. > > As Paul explained, in system mode there are other things that > can cause interrupts, which you can't disable (unless you have > your own emulated OS). I am interested in which interrupts might occur, and how they influence the instruction count. I am not using any input, and all output is sent to the serial port via "-serial stdout". I have a small assembler loop like the following pseudo code: NOP mov R1, $1000 loop: subs R1, $1 bne loop NOP On every NOP Qemu prints the instruction count. By turning of all timers in Qemu I hope to disable all timer interrupts for the guest. The results I get are not correct for the first time the code is run, but for all subsequent runs. In the first run, the instruction count has 12 additional instructions, which are not actually executed. What is the cause of those additional instructions? Greetings, Steffen