From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=42499 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PKggl-0000MJ-1B for qemu-devel@nongnu.org; Mon, 22 Nov 2010 19:25:01 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PKgga-0006HX-JR for qemu-devel@nongnu.org; Mon, 22 Nov 2010 19:24:50 -0500 Received: from e1.ny.us.ibm.com ([32.97.182.141]:55841) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PKgga-0006H5-EC for qemu-devel@nongnu.org; Mon, 22 Nov 2010 19:24:40 -0500 Received: from d01relay02.pok.ibm.com (d01relay02.pok.ibm.com [9.56.227.234]) by e1.ny.us.ibm.com (8.14.4/8.13.1) with ESMTP id oAN0GjoI026759 for ; Mon, 22 Nov 2010 19:16:45 -0500 Received: from d03av05.boulder.ibm.com (d03av05.boulder.ibm.com [9.17.195.85]) by d01relay02.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id oAN0OarE463276 for ; Mon, 22 Nov 2010 19:24:37 -0500 Received: from d03av05.boulder.ibm.com (loopback [127.0.0.1]) by d03av05.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id oAN0Oa1C023449 for ; Mon, 22 Nov 2010 17:24:36 -0700 Message-ID: <4CEB09BD.2010804@linux.vnet.ibm.com> Date: Mon, 22 Nov 2010 18:24:29 -0600 From: Anthony Liguori MIME-Version: 1.0 References: <1290466818-5230-1-git-send-email-aliguori@us.ibm.com> <20101122230405.GB10050@sequoia.sous-sol.org> <4CEB006C.8010407@linux.vnet.ibm.com> <20101122235651.GD10050@sequoia.sous-sol.org> In-Reply-To: <20101122235651.GD10050@sequoia.sous-sol.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: [PATCH] qemu-kvm: introduce cpu_start/cpu_stop commands List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Chris Wright Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org On 11/22/2010 05:56 PM, Chris Wright wrote: > * Anthony Liguori (aliguori@linux.vnet.ibm.com) wrote: > >> On 11/22/2010 05:04 PM, Chris Wright wrote: >> >>> * Anthony Liguori (aliguori@us.ibm.com) wrote: >>> >>>> qemu-kvm vcpu threads don't response to SIGSTOP/SIGCONT. Instead of teaching >>>> them to respond to these signals, introduce monitor commands that stop and start >>>> individual vcpus. >>>> >>> In the past SIGSTOP has introduced time skew. Have you verified this >>> isn't an issue. >>> >> Time skew is a big topic. Are you talking about TSC drift, >> pit/rtc/hpet drift, etc? >> > Sorry to be vague, but it's been long enough that I don't recall > the details. The guest kernel's clocksource effected how timekeeping > progressed across STOP/CONT (was probably missing qemu based timer ticks). > While this is not the same, made me wonder if you'd tested against that. > Yeah, it's definitely going to increase the likelihood of interrupt coalescing but only as much as a contended CPU would already. QEMU will keep getting timer ticks but the guest won't process them in a timely fashion. >> It's certainly going to stress periodic interrupt catch up code. >> > Heh, call it a feature for autotest ;) > Excellent idea :-) Regards, Anthony Liguori > thanks, > -chris >