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Re: NetBSD/Xen samba performance low (compared to NetBSD/amd64)

Matthias Petermann <> writes:

> Constellation 1 (Pure NetBSD kernel):
> * NetBSD/amd64 9.0 Kernel + Samba: throughput ~60 MByte/s
> Constellation 2 (NetBSD/Xen Domain 0):
> * Xen 4.11 + NetBSD/Xen Dom0 + Samba: throughput ~12 MByte/s
> I measured this by copying an 8 GB ISO file from a Windows host.
> In constellation 2, no guests had started and the full main memory of
> Dom0 was assigned. In my view, the only significant difference is that
> NetBSD can only use one of the two CPU cores under Xen. Since the CPU
> was idle on average at 20% during copying, that doesn't seem to be the
> bottleneck?
> Are such differences in I/O performance to be expected?

Other than the 1 cpu vs ? cpus, no.   I tested xen perfmorance long ago,
in 2006 with a setup

  NetBSD dom0
  disk file in filesystem
  NetBSD domU with xbd0 from the file

 and found that reading with dd:

   the dom0 raw disk was just about the same as bare metal

   the file was maybe 5-10% slower (maybe not quite; it was noticeable but
   not a big deal)

   the xbd0d "raw disk" was also 5-10 % slower than reading the file in
   the dom0

Now, this isn't what you asked, but I find the difference you found seem
like a bug.

I would definitely do dd from the raw disk in your case 1 and 2,
followed by dd of the iso.

Also, I would repeat your tests and run "systat vmstat" during each
case, and also netstat to see if the network interface is not keeping
up.   Then I would run iperf, ttcp or whatever to test network separate
from samba and disk.


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