Re: Dom0 bad network performance (was: NetBSD/Xen samba performance low (compared to NetBSD/amd64))

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Sat, Feb 13, 2021 at 05:03:59AM +0100, Matthias Petermann wrote:
> Hello all,
> 
> last summer I already had a request here, which I had classified as a Samba
> problem at that time due to insufficient preliminary investigations. You
> guys helped me a lot to investigate the problem further, but unfortunately I
> didn't have the chance to follow up on it.
> 
> Now I have made a new attempt on the same hardware (Intel NUC5) and have
> gone a little deeper into the matter. My new findings are:
> 
>  - the raw read/write performance in the filesystem is hardly different, no
> matter if I use NetBSD as Dom0 or on the same system a "pure" NetBSD kernel
> without Xen. In both cases it is about 60 MByte/s which appears ok for this
> type of hardware.
> 
>  - when transferring files of this file system over the network the
> performance is lost - with NetBSD as Dom0 the transfer rate is max. 12
> MByte/s, while it is about 60 MByte/s when using a "pure" NetBSD kernel
> without Xen. It does not matter whether the transfer is done with Samba or
> another protocol (sftp, NFS).

I noticed this too, but never took the time to investigate.
At first glance it could be an issue with latency, which is highter
with a dom0 setup than with bare metal (the kernel/userland boundary is
much more costly for dom0).

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--