From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: nested KVM slower than QEMU with gnumach guest kernel Date: Mon, 17 Nov 2014 11:21:22 +0200 Message-ID: <20141117092122.GF26187@minantech.com> References: <20141111185515.GA16376@type.youpi.perso.aquilenet.fr> <54629EFC.1050307@web.de> <20141116221828.GA13123@type> <20141117085845.GE26187@minantech.com> <20141117090342.GP3110@type.youpi.perso.aquilenet.fr> <5469BA25.2090204@web.de> <20141117091025.GS3110@type.youpi.perso.aquilenet.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE To: Samuel Thibault , Jan Kiszka , kvm@vger.kernel.org, pbonzini@redhat.com Return-path: Received: from mail-wi0-f176.google.com ([209.85.212.176]:51276 "EHLO mail-wi0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751300AbaKQJV0 convert rfc822-to-8bit (ORCPT ); Mon, 17 Nov 2014 04:21:26 -0500 Received: by mail-wi0-f176.google.com with SMTP id ex7so5006076wid.9 for ; Mon, 17 Nov 2014 01:21:25 -0800 (PST) Content-Disposition: inline In-Reply-To: <20141117091025.GS3110@type.youpi.perso.aquilenet.fr> Sender: kvm-owner@vger.kernel.org List-ID: On Mon, Nov 17, 2014 at 10:10:25AM +0100, Samuel Thibault wrote: > Jan Kiszka, le Mon 17 Nov 2014 10:04:37 +0100, a =C3=A9crit : > > On 2014-11-17 10:03, Samuel Thibault wrote: > > > Gleb Natapov, le Mon 17 Nov 2014 10:58:45 +0200, a =C3=A9crit : > > >> Do you know how gnumach timekeeping works? Does it have a timer = that fires each 1ms? > > >> Which clock device is it using? > > >=20 > > > It uses the PIT every 10ms, in square mode > > > (PIT_C0|PIT_SQUAREMODE|PIT_READMODE =3D 0x36). > >=20 > > Wow... how retro. That feature might be unsupported - does user spa= ce > > irqchip work better? >=20 > I had indeed tried giving -machine kernel_irqchip=3Doff to the L2 kvm= , > with the same bad performance and external_interrupt in the trace. >=20 They are always be in the trace, but do you see them each ms or each 10= ms with user space irqchip? -- Gleb.