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

[Roger Pau Monné]

On Tue, Aug 16, 2016 at 12:13:55PM +0200, rainer at ultra-secure.de wrote:
> Am 2016-08-16 12:06, schrieb Roger Pau Monné:
> > On Tue, Aug 16, 2016 at 11:29:43AM +0200, rainer at ultra-secure.de wrote:
> > > Am 2016-08-16 10:54, schrieb 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?
> > > >
> > > 
> > > This is both Xen.
> > > I think the customer is also running it on some sort of
> > > virtualization.
> > 
> > Hm, so a given workload on Xen takes ~9s, and it also takes ~9s when run
> > on
> > bare metal FreeBSD, is that right?
> 
> 
> It only takes 9s with Linux as a Xen-guest.
> With all things equal (PHP-version, MariaDB-version), FreeBSD is essentially
> only half as fast as Linux as a Xen-guest.
> Sorry for the confusion.
> 

And FreeBSD on bare metal is equally fast as Linux then? (ie: the slowdown 
is only noticeable when running FreeBSD on Xen)

> 
> > > > hw.xen.disable_pv_disks=1
> > > > hw.xen.disable_pv_nics=1
> > > 
> > > OK, can I still boot the VM with this or will NICs and disks show up
> > > as
> > > different devices then?
> > 
> > NIC will show up as "re", disks as "ada" (which is what you already
> > have).
> 
> I tried this with the FreeBSD 11 VM mentioned in my other mail and it only
> gets a bit slower.
> Between 5% and 10%, I'd say.

If you can provide me with some way to synthesize this workload that doesn't 
involve setting up the full stack plus your app I can try to reproduce it 
locally and analyze it in order to find the bottlenecks.

Roger.