Xen performance on FreeBSD vs Linux

[Stefan Parvu]

Hi,

How Xen hypervisor compares in terms of performance (guest) on FreeBSD vs Linux
, using ZFS or UFS ? Are there any benchmarks or tests regarding this ?

Thanks

Stefan Parvu
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[Roger Pau Monné]

On Mon, Jan 06, 2020 at 12:43:51PM +0200, Stefan Parvu wrote:
> Hi,
>
> How Xen hypervisor compares in terms of performance (guest) on FreeBSD vs Linux
> , using ZFS or UFS ?

There are several factors to take into account here.

On FreeBSD the hypervisor is built with clang, while on Linux it's
usually built with gcc, and hence different optimizations will be
used.

Also a FreeBSD dom0 can only work in PVH mode, which is faster for
certain operations like page table modifications, but it's slower for
others, like issuing hypercalls, when compared to a PV dom0.

I don't have figures at hand now, but guest creation is likely slower
on a FreeBSD PVH dom0 than on a Linux PV dom0, and that's because
hypercalls are more expensive on PVH than on PV (has nothing to do
whether Linux or FreeBSD is used).

> Are there any benchmarks or tests regarding this ?

I don't think so, but I think they will be useful if someone has the
time to perform them :).

Thanks, Roger.
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[Stefan Parvu]

>
> Also a FreeBSD dom0 can only work in PVH mode, which is faster for
> certain operations like page table modifications, but it's slower for
> others, like issuing hypercalls, when compared to a PV dom0.
>
> I don't have figures at hand now, but guest creation is likely slower
> on a FreeBSD PVH dom0 than on a Linux PV dom0, and that's because
> hypercalls are more expensive on PVH than on PV (has nothing to do
> whether Linux or FreeBSD is used).

right. thanks a lot for pointers. A bit confusing is that I see mentioned
around that Xen of FreeBSD is experimental. Is this true ?

I will have 2 servers to test Xen and Bhyve on FreeBSD 12.1 and check how
well the hypervisors work for different guest from Linux, BSD and Windows.

Im more interested on bhyve vs Xen on FreeBSd than Linux. We will keep
FreeBSD as our main virtualization platform.

Stefan
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[mail-4]

Am So., 12. Jan. 2020 um 20:07 Uhr schrieb Stefan Parvu <
[hidden email]>:

> >
> > Also a FreeBSD dom0 can only work in PVH mode, which is faster for
> > certain operations like page table modifications, but it's slower for
> > others, like issuing hypercalls, when compared to a PV dom0.
> >
> > I don't have figures at hand now, but guest creation is likely slower
> > on a FreeBSD PVH dom0 than on a Linux PV dom0, and that's because
> > hypercalls are more expensive on PVH than on PV (has nothing to do
> > whether Linux or FreeBSD is used).
>
> right. thanks a lot for pointers. A bit confusing is that I see mentioned
> around that Xen of FreeBSD is experimental. Is this true ?
>
> I will have 2 servers to test Xen and Bhyve on FreeBSD 12.1 and check how
> well the hypervisors work for different guest from Linux, BSD and Windows.
>
> Im more interested on bhyve vs Xen on FreeBSd than Linux. We will keep
> FreeBSD as our main virtualization platform.
>
> Stefan

FreeBSD as Dom0 feels (at least ~6 month ago) really somehow experimental
compared to my linux experience. i would go the bhyve route if your
hardware supports the required cpu features.
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[Roger Pau Monné]

On Sun, Jan 12, 2020 at 09:07:32PM +0200, Stefan Parvu wrote:

> >
> > Also a FreeBSD dom0 can only work in PVH mode, which is faster for
> > certain operations like page table modifications, but it's slower for
> > others, like issuing hypercalls, when compared to a PV dom0.
> >
> > I don't have figures at hand now, but guest creation is likely slower
> > on a FreeBSD PVH dom0 than on a Linux PV dom0, and that's because
> > hypercalls are more expensive on PVH than on PV (has nothing to do
> > whether Linux or FreeBSD is used).
>
> right. thanks a lot for pointers. A bit confusing is that I see mentioned
> around that Xen of FreeBSD is experimental. Is this true ?

PVH dom0 support in Xen is experimental, the FreeBSD PVH bits are
mostly stable and I wouldn't expect many changes there except from
bug fixes. The PVH guest ABI is also stable since quite some time
ago.

Thanks, Roger.
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[Roger Pau Monné]

On Mon, Jan 13, 2020 at 02:51:16PM +0100, Juergen Gotteswinter wrote:

> Am So., 12. Jan. 2020 um 20:07 Uhr schrieb Stefan Parvu <
> [hidden email]>:
>
> > >
> > > Also a FreeBSD dom0 can only work in PVH mode, which is faster for
> > > certain operations like page table modifications, but it's slower for
> > > others, like issuing hypercalls, when compared to a PV dom0.
> > >
> > > I don't have figures at hand now, but guest creation is likely slower
> > > on a FreeBSD PVH dom0 than on a Linux PV dom0, and that's because
> > > hypercalls are more expensive on PVH than on PV (has nothing to do
> > > whether Linux or FreeBSD is used).
> >
> > right. thanks a lot for pointers. A bit confusing is that I see mentioned
> > around that Xen of FreeBSD is experimental. Is this true ?
> >
> > I will have 2 servers to test Xen and Bhyve on FreeBSD 12.1 and check how
> > well the hypervisors work for different guest from Linux, BSD and Windows.
> >
> > Im more interested on bhyve vs Xen on FreeBSd than Linux. We will keep
> > FreeBSD as our main virtualization platform.
> >
> > Stefan
>
>
> FreeBSD as Dom0 feels (at least ~6 month ago) really somehow experimental
> compared to my linux experience.

Hello,

Can you give us more details regarding this comment, and what did you
feel was missing or could be improved compared to Linux?

Thanks, Roger.
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