From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:48916) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TEayH-0002YS-M1 for qemu-devel@nongnu.org; Thu, 20 Sep 2012 03:14:55 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TEayB-0006Ya-Sg for qemu-devel@nongnu.org; Thu, 20 Sep 2012 03:14:49 -0400 Received: from goliath.siemens.de ([192.35.17.28]:31551) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TEayB-0006YL-If for qemu-devel@nongnu.org; Thu, 20 Sep 2012 03:14:43 -0400 Message-ID: <505AC257.3080000@siemens.com> Date: Thu, 20 Sep 2012 09:14:31 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <50587258.9090303@siemens.com> <20120919133720.GB22659@snow> <5059D26E.2050808@siemens.com> <5059DAC4.9020907@siemens.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] Will the ELI incorporated in theKVM? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Abel Gordon Cc: Nadav Har'El , GaoYi , "qemu-devel@nongnu.org" , Michael D Day , Avi Kivity , Muli Ben-Yehuda , Nadav Amit On 2012-09-20 08:58, Abel Gordon wrote: > > > GaoYi wrote on 20/09/2012 08:42:51 AM: > >> The CPU isolation in Hitachi patches is just to improve the real >> time performance of GUEST. The core of it, direct IRQ delivery, is >> very similar to that of ELI. >> For the ELI patches, >> (1) Since EOI part of ELI is already supported by the Intel >> Sandy Bridge CPUs and requires modifications on GUEST code, it >> should not be included in the KVM. Only the ELI delivery part, which >> plays a vital role in performance improvement, should be considered. > > Giving to the guest direct access to the EOI MSR (if x2APIC is available) > is what we call "ELI completion". Note this mechanism is not so simple, > there are some cases (which are not part of the critical path) where ELI > must trap > EOIs. For the APLOS paper evaluation we didn't have CPUs with x2APIC so we > simulated the behavior changing the guest code. > In any case, as you can see in the paper, the big part of the improvement > comes from "ELI delivery". "ELI completion" improvement will be > even smaller with the latest KVM EOI optimizations for the memory based > LAPIC. > >> (2) It should be provided in the kvm-kmod or qemu-kvm ( not just >> for some linux kernel as Hitachi patches do), to make this part >> independent of linux kernel version. > > Exactly, ELI only modifies the kvm kernel module and qemu-kvm but we should > also modify VFIO for newer kvm versions. Again: If you think the feature is non-invasive, send patches against the kernel and QEMU. Jan -- Siemens AG, Corporate Technology, CT RTC ITP SDP-DE Corporate Competence Center Embedded Linux