From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Marchand Subject: Re: [Qemu-devel] Why I advise against using ivshmem Date: Tue, 17 Jun 2014 11:03:32 +0200 Message-ID: <53A00464.8090609@6wind.com> References: <20140610184818.2e490419@nbschild1> <53978375.6090707@6wind.com> <87ppie1v4r.fsf@blackfin.pond.sub.org> <20140612094413.15e56938@nbschild1> <87vbs6qjhj.fsf_-_@blackfin.pond.sub.org> <5399CF09.8030803@6wind.com> <87ppidnqmy.fsf@blackfin.pond.sub.org> <539AC3E0.9090404@6wind.com> <539ACDE6.7020709@redhat.com> <539AFF7C.7090702@6wind.com> <539B064D.2050501@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Vincent JARDIN , Henning Schild , Olivier MATZ , kvm , qemu-devel , Linux Virtualization , "thomas.monjalon@6wind.com" To: Stefan Hajnoczi , Paolo Bonzini Return-path: Received: from mail-we0-f176.google.com ([74.125.82.176]:48971 "EHLO mail-we0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755264AbaFQJDi (ORCPT ); Tue, 17 Jun 2014 05:03:38 -0400 Received: by mail-we0-f176.google.com with SMTP id u56so6940987wes.35 for ; Tue, 17 Jun 2014 02:03:37 -0700 (PDT) In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: Hello all, On 06/17/2014 04:54 AM, Stefan Hajnoczi wrote: > ivshmem has a performance disadvantage for guest-to-host > communication. Since the shared memory is exposed as PCI BARs, the > guest has to memcpy into the shared memory. > > vhost-user can access guest memory directly and avoid the copy inside the guest. Actually, you can avoid this memory copy using frameworks like DPDK. > Unless someone steps up and maintains ivshmem, I think it should be > deprecated and dropped from QEMU. Then I can maintain ivshmem for QEMU. If this is ok, I will send a patch for MAINTAINERS file. -- David Marchand From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38988) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WwpIw-0005pq-I2 for qemu-devel@nongnu.org; Tue, 17 Jun 2014 05:03:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WwpIp-0000oo-3R for qemu-devel@nongnu.org; Tue, 17 Jun 2014 05:03:46 -0400 Received: from mail-wi0-f177.google.com ([209.85.212.177]:50368) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WwpIo-0000lG-TS for qemu-devel@nongnu.org; Tue, 17 Jun 2014 05:03:39 -0400 Received: by mail-wi0-f177.google.com with SMTP id r20so5403341wiv.16 for ; Tue, 17 Jun 2014 02:03:37 -0700 (PDT) Message-ID: <53A00464.8090609@6wind.com> Date: Tue, 17 Jun 2014 11:03:32 +0200 From: David Marchand MIME-Version: 1.0 References: <20140610184818.2e490419@nbschild1> <53978375.6090707@6wind.com> <87ppie1v4r.fsf@blackfin.pond.sub.org> <20140612094413.15e56938@nbschild1> <87vbs6qjhj.fsf_-_@blackfin.pond.sub.org> <5399CF09.8030803@6wind.com> <87ppidnqmy.fsf@blackfin.pond.sub.org> <539AC3E0.9090404@6wind.com> <539ACDE6.7020709@redhat.com> <539AFF7C.7090702@6wind.com> <539B064D.2050501@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] Why I advise against using ivshmem List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi , Paolo Bonzini Cc: Henning Schild , Olivier MATZ , kvm , qemu-devel , Linux Virtualization , Vincent JARDIN , "thomas.monjalon@6wind.com" Hello all, On 06/17/2014 04:54 AM, Stefan Hajnoczi wrote: > ivshmem has a performance disadvantage for guest-to-host > communication. Since the shared memory is exposed as PCI BARs, the > guest has to memcpy into the shared memory. > > vhost-user can access guest memory directly and avoid the copy inside the guest. Actually, you can avoid this memory copy using frameworks like DPDK. > Unless someone steps up and maintains ivshmem, I think it should be > deprecated and dropped from QEMU. Then I can maintain ivshmem for QEMU. If this is ok, I will send a patch for MAINTAINERS file. -- David Marchand