Re: Diagnosing virtual machine network issues

On 7/30/24 11:15, Alex Arslan wrote:
> Some progress on this front...
> 
>> On Jul 19, 2024, at 9:08 AM, Alex Arslan <ararslan@comcast.net> wrote:
>>
>>> If it happens frequently and you think it might be the network, perhaps try with the Intel em driver instead of the virtio network driver ?
> 
> I forgot to mention, we swapped the virtio network device to the Intel
> e1000 device but haven't observed any difference.
> 
> I did manage to narrow down the issue to a more minimal reproducer, which
> is just a simple request to the invalid domain using libcurl, but with a
> 30-second timeout. (The Julia code sets that timeout internally.) I tried
> compiling the reproducer and running the executable wrapped with `time`
> separately in the FreeBSD VM and on the Linux host. In the VM, it actually
> sits and waits out the 30 seconds then errors with a timeout, and `time`
> reports a real time of 30.289 seconds. On the host, it's instantaneous;
> the resolution failure is reported immediately. I then tried setting the
> timeout in the VM to 31 seconds, and it produces the expected resolution
> failure with a real time of 30.420 seconds. I don't understand what's
> going on here...
> 

Can you provide more context?  I'm not seeing earlier messages anywhere 
in my email folders.  Is this a Qemu issue?

Coincidentally, I'm experimenting with FreeBSD under Qemu on my Mac Mini 
M1 and seeing about 93 mbits/sec in iperf, regardless of the NIC 
configured.  ( VM to bare metal host )  Bare metal to bare metal shows 
930 mbits/sec.

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