From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [Qemu-devel] [PATCH] kvm: Set default accelerator to "kvm" if the host supports it Date: Mon, 01 Oct 2012 15:07:48 -0500 Message-ID: <87lifqufaj.fsf@codemonkey.ws> References: <836856249.4545946.1349119506235.JavaMail.root@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kiszka , kvm , Scott Moser , Marcelo Tosatti , Michael Tokarev , qemu-devel , Bruce Rogers , Avi Kivity , Cole Robinson , "Daniel P. Berrange" , Andreas =?utf-8?Q?F=C3=A4rber?= To: Paolo Bonzini Return-path: Received: from mail-oa0-f46.google.com ([209.85.219.46]:37042 "EHLO mail-oa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751068Ab2JAUHw (ORCPT ); Mon, 1 Oct 2012 16:07:52 -0400 Received: by oagh16 with SMTP id h16so5499211oag.19 for ; Mon, 01 Oct 2012 13:07:52 -0700 (PDT) In-Reply-To: <836856249.4545946.1349119506235.JavaMail.root@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Paolo Bonzini writes: >> But libguest can set it's accelerator option to whatever it wants. >> >> If your running QEMU under a VM, it's pretty reasonable to have to >> use a special option IMHO. > > It's also reasonable to have consecutive releases change defaults in > a more "friendly" way (i.e. from tcg to kvm:tcg), especially since > we'll get users that formerly used qemu-kvm and never had to specify > neither -machine accel nor --enable-kvm. I agree with you except for the 'kvm:tcg' part. > >> > IMHO, default to KVM, fallback to TCG is the most friendly default >> > behaviour. >> >> Except if a user expects good network performance and can't >> understand why they're getting 100kb/s. > > libguestfs doesn't need network at all (though I wonder if they could > use lxc instead...). FWIW, libguestfs already uses -machine accel=kvm:tcg so we can completely the libguestfs use-case for this discussion. Regards, Anthony Liguori > > Paolo From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:50601) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TImHS-0007Ig-52 for qemu-devel@nongnu.org; Mon, 01 Oct 2012 16:07:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TImHQ-0000tP-VG for qemu-devel@nongnu.org; Mon, 01 Oct 2012 16:07:54 -0400 Received: from mail-oa0-f45.google.com ([209.85.219.45]:60579) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TImHQ-0000tL-QI for qemu-devel@nongnu.org; Mon, 01 Oct 2012 16:07:52 -0400 Received: by oagi18 with SMTP id i18so5215891oag.4 for ; Mon, 01 Oct 2012 13:07:52 -0700 (PDT) From: Anthony Liguori In-Reply-To: <836856249.4545946.1349119506235.JavaMail.root@redhat.com> References: <836856249.4545946.1349119506235.JavaMail.root@redhat.com> Date: Mon, 01 Oct 2012 15:07:48 -0500 Message-ID: <87lifqufaj.fsf@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Subject: Re: [Qemu-devel] [PATCH] kvm: Set default accelerator to "kvm" if the host supports it List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: kvm , Scott Moser , Jan Kiszka , Marcelo Tosatti , Michael Tokarev , qemu-devel , Bruce Rogers , Avi Kivity , Cole Robinson , Andreas =?utf-8?Q?F=C3=A4rber?= Paolo Bonzini writes: >> But libguest can set it's accelerator option to whatever it wants. >> >> If your running QEMU under a VM, it's pretty reasonable to have to >> use a special option IMHO. > > It's also reasonable to have consecutive releases change defaults in > a more "friendly" way (i.e. from tcg to kvm:tcg), especially since > we'll get users that formerly used qemu-kvm and never had to specify > neither -machine accel nor --enable-kvm. I agree with you except for the 'kvm:tcg' part. > >> > IMHO, default to KVM, fallback to TCG is the most friendly default >> > behaviour. >> >> Except if a user expects good network performance and can't >> understand why they're getting 100kb/s. > > libguestfs doesn't need network at all (though I wonder if they could > use lxc instead...). FWIW, libguestfs already uses -machine accel=kvm:tcg so we can completely the libguestfs use-case for this discussion. Regards, Anthony Liguori > > Paolo