Re: 2nd round of xen benchmarking

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Mon, Aug 05, 2024 at 06:35:09PM -0400, Greg Troxel wrote:
> I have swapped out one ancient system for another.  This one has VMX
> feature, but doesn't have the more modern virtualization features.
> 
> The basic benchmark is building devel/m4, no ccache, MAKE_JOBS=1, work
> on tmpfs.  1 vcpu for dom0 and domU.  (Multiple CPUs on bare metal, but
> MAKE_JOBS=1.)
> 
> Overall, it looks like (talking about times) commpared to bare metal times:
> 
>   dom0 is 2x
>   pv (or pvh/pvshim) domU is about 3x
> 
>   n9-amd64: hvm is 19x (!!!!)
> 
>   n10-amd64: pvh is 4.5 slower than pv, and pvhvm is 4x slower than pv
> 
> It remains a really good question if the newer CPUs will lead to reduced
> slowdowns.   As it is, pvh is a win for n10-i386, and other than that,
> pv is best, sometimes by a huge amount.

For PVH to be a win, my guess is that you really want a CPU with EPT. 
Otherwise each page table operation (and pkgsrc does a lot of fork/exec)
causes a trap to the hypervisor. PV page table operations is cheaper.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--