netdev - Re: [PATCH net] selftests: net: add missing config for big tcp tests

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Message-ID: <785a9d7b1ce68f8131e6f9c8802981ac7ad75948.camel@redhat.com>
Date: Tue, 30 Jan 2024 19:41:10 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, Shuah Khan <shuah@...nel.org>, Xin Long
 <lucien.xin@...il.com>,  Florian Westphal <fw@...len.de>, Aaron Conole
 <aconole@...hat.com>, Nikolay Aleksandrov <razor@...ckwall.org>,
 linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net] selftests: net: add missing config for big tcp tests

On Mon, 2024-01-29 at 08:39 -0800, Jakub Kicinski wrote:
> On Mon, 29 Jan 2024 17:31:33 +0100 Paolo Abeni wrote:
> > Uhm... while the self-test doesn't emit anymore the message related to
> > the missing modules, it still fails in the CI env and I can't reproduce
> > the failures in my local env (the same for the gro.sh script).
> > 
> > If I understand correctly, the tests run under double virtualization (a
> > VM on top AWS?), is that correct? I guess the extra slowdown/overhead
> > will need more care.
> 
> Yes, it's VM inside a VM without nested virtualization support.
> A weird setup, granted, but when we move to bare metal I'd like
> to enable KASAN, which will probably cause a similar slowdown..
> 
> You could possibly get a similar slowdown by disabling HW virt /
> KVM?

Thanks, the above helped - that is, I can reproduce the failure running
the self-tests in a VM with KVM disabled in the host. Funnily enough I
can't use plain virtme for that - the virtme VM crashes on boot,
possibly due to the wrong 'machine' argument passed to qemu.

In any case I can't see a sane way to cope with such slow environments
except skipping the sensitive cases.

> FWIW far the 4 types of issues we've seen were:
>  - config missing
>  - OS doesn't ifup by default
>  - OS tools are old / buggy
>  - VM-in-VM is just too slow.
> 
> There's a bunch of failures in forwarding which look like perf issues.
> I wonder if we should introduce something in the settings file to let
> tests know that they are running in very slow env?

I was wondering about passing such info to the test e.g. via an env
variable:

vng --run . --user root -- HOST_IS_DAMN_SLOW=true
./tools/testing/selftests/kselftest_install/run_kselftest.sh -t
<whatever>

In any case some tests should be updated to skip the relevant cases
accordingly, right?

Cheers,

Paolo