Is it me or is FreeBSD slower on Xen than Linux?

[Roger Pau Monné]

On Mon, Aug 15, 2016 at 05:54:52PM +0200, rainer at ultra-secure.de wrote:
> Hi,
> 
> I've got a problem.
> 

Hello,
 
> 
> For a customer, I run a VM in Xen that should perform a certain task in PHP
> (written using the ZendFrameWork).
> 
> That task takes about 18-20 seconds on FreeBSD 10.3 amd64, MariaDB 5.5.0,
> php 5.5.37 in a VM that has 8 vCPUs and 16GB of memory
> The "reference" server that the customer uses is somewhere else and manages
> to perform the same task in 3s.
> 
> I've tried this with FreeBSD 10.3, PHP7.0 and MariaDB 10.1 and it takes
> about 9s.

In the sentence above, are you running it in a Xen VM or on bare metal?

> I've tried it on physical hardware with 10.3, PHP5.5, MariaDB 5.5 and it
> also takes about 9s (that machine hosts a load of other sites but has lot of
> cores and memory available).
> 
> 
> Then, I've installed an Ubuntu 14 VM in XenServer. It comes with PHP5.5 and
> MariaDB 5.5 by default. It's VM with 2vCPUs and 8GB RAM.
> 
> There, the script take about 9s, too (just as if it was running on physical
> FreeBSD).

I'm not sure I understood your problem right, is it that FreeBSD on Xen 
always takes 18-20s to perform a task while on bare metal it only takes ~9s?

If that's the case, I would recommend that you first try to disable PV disks 
and nics, by adding the following to your /boot/loader.conf:

hw.xen.disable_pv_disks=1
hw.xen.disable_pv_nics=1

If that still yelds the same performance (or worse), then you could still 
try to disable all Xen code, by removing:

options 	XENHVM
device		xenpci

>From you kernel config and recompiling the kernel.

Roger.