From owner-freebsd-virtualization@FreeBSD.ORG  Thu Jan 16 16:59:58 2014
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Date: Thu, 16 Jan 2014 17:59:53 +0100
From: =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= <roger.pau@citrix.com>
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To: Sydney Meyer <meyer.sydney@googlemail.com>,
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Subject: Re: Xen PVHVM with FreeBSD10 Guest
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On 16/01/14 17:41, Sydney Meyer wrote:
> Hello everyone,
> 
> does someone know how to check if the paravirtualized I/O drivers from Xen are loaded/working in FreeBSD 10? To my understanding it isn't necessary anymore to compile a custom kernel with PVHVM enabled, right? In /var/log/messages/ I can see the XN* and XBD* devices and the network performance is very good (saturated Gb) compared to qemu-emulated, but the disk performance is not as well, infact, it is even slower than emulated with qemu (0.10.2). I did some test with dd and bonnie++, turned caching on the host off and tried to directly sync to disk, PVonHVM is averagely 15-20 % slower than QEMU at throughput. Both VM's are running on the same host on a Xen 4.1 Hypervisor with QEMU 0.10.2 on a Debian Linux 3.2 Kernel as Dom0.

PV drivers will be used automatically if Xen is detected. You should see
something like this on dmesg:

xn0: <Virtual Network Interface> at device/vif/0 on xenbusb_front0
xn0: Ethernet address: 00:16:3e:47:d4:52
xenbusb_back0: <Xen Backend Devices> on xenstore0
xn0: backend features: feature-sg feature-gso-tcp4
xbd0: 20480MB <Virtual Block Device> at device/vbd/51712 on xenbusb_front0
xbd0: features: flush, write_barrier
xbd0: synchronize cache commands enabled.

Are you using a raw file as a disk?

Roger.