From mboxrd@z Thu Jan 1 00:00:00 1970 From: Samuel Thibault Subject: Re: nested KVM slower than QEMU with gnumach guest kernel Date: Mon, 17 Nov 2014 10:37:28 +0100 Message-ID: <20141117093728.GA3953@type.bordeaux.inria.fr> 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> <20141117092122.GF26187@minantech.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Jan Kiszka , kvm@vger.kernel.org, pbonzini@redhat.com To: Gleb Natapov Return-path: Received: from mail2-relais-roc.national.inria.fr ([192.134.164.83]:20740 "EHLO mail2-relais-roc.national.inria.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751962AbaKQJha (ORCPT ); Mon, 17 Nov 2014 04:37:30 -0500 Content-Disposition: inline In-Reply-To: <20141117092122.GF26187@minantech.com> Sender: kvm-owner@vger.kernel.org List-ID: Gleb Natapov, le Mon 17 Nov 2014 11:21:22 +0200, a =E9crit : > 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 =E9crit : > > > On 2014-11-17 10:03, Samuel Thibault wrote: > > > > Gleb Natapov, le Mon 17 Nov 2014 10:58:45 +0200, a =E9crit : > > > >> Do you know how gnumach timekeeping works? Does it have a time= r 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 s= pace > > > irqchip work better? > >=20 > > I had indeed tried giving -machine kernel_irqchip=3Doff to the L2 k= vm, > > 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 = 10ms > with user space irqchip? The external interupts are every 1 *microsecond, not millisecond. With irqchip=3Doff or not. Samuel