Re: [Qemu-devel] [PATCH v4 09/11] tests/vm: netbsd autoinstall, using serial console

["Daniel P. Berrangé" <berrange@redhat.com>]

On Fri, Jul 05, 2019 at 11:52:20AM +0100, Peter Maydell wrote:
> On Fri, 5 Jul 2019 at 11:43, Kamil Rytarowski <n54@gmx.com> wrote:
> >
> > On 05.07.2019 12:24, Alex Bennée wrote:
> > >
> > > Gerd Hoffmann <kraxel@redhat.com> writes:
> > >
> > >> Instead of fetching the prebuilt image from patchew download the install
> > >> iso and prepare the image locally.  Install to disk, using the serial
> > >> console.  Create qemu user, configure ssh login.  Install packages
> > >> needed for qemu builds.
> > >
> > > I've had to drop this from my v3 PR as Peter was seeing a very
> > > slow/hanging install when running his merge tests. I've tried to
> > > reproduce and I see it stall while installing packages but nowhere near
> > > the delay Peter has seen.
> > >
> > > Any pointers on how to debug gratefully received.
> > >
> >
> > Does it use virtio? There were performance issues with virio disk device.
> 
> The symptoms I see with this patch are that the VM appears to
> completely stall, rather than progressing but slowly.
> (I do also see on the current NetBSD tests/vm setup that sometimes
> 'make check' runs pretty slowly, but in that case it does make
> progress, it just completes much slower than either the openbsd
> or freebsd VMs. 'make check' is not particularly IO intensive,
> certainly not compared to the actual compile phase, though.
> And sometimes the initial "wait for VM to boot and ssh in"
> phase just hits our 6 minute timeout.)

I wonder if there's some undiagnosed timer or interrupt problems we're
hitting in NetBSD. We had someone just yesterdayt on IRC reporting they
needed kernel irqchip disabled for OpenBSD under some circumstances
for example. So could be worth trying one or more of the various
tweak args like:

    -machine kernel_irqchip=off
    -global kvm-pit.lost_tick_policy=discard

to see if it affects stability to any useful extent.

Regards,
Daniel
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