From mboxrd@z Thu Jan  1 00:00:00 1970
From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Subject: Re: nested KVM slower than QEMU with gnumach guest kernel
Date: Mon, 17 Nov 2014 10:10:25 +0100
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Cc: Gleb Natapov <gleb@kernel.org>, kvm@vger.kernel.org,
	pbonzini@redhat.com
To: Jan Kiszka <jan.kiszka@web.de>
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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 timer th=
at 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 space
> irqchip work better?

I had indeed tried giving -machine kernel_irqchip=3Doff to the L2 kvm,
with the same bad performance and external_interrupt in the trace.

Samuel