Re: [Xen-devel] [PATCH V4] xen/arm: domain_build: allocate lowmem for dom0 as much as possible

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 17 Nov 2016, Stefano Stabellini wrote:
> > > I have just run the numbers on ARM64 (APM m400) and it is still much
> > > faster than netfront/netback. This is what I get by running iperf -c in
> > > a VM and iperf -s in Dom0:
> > >
> > >         PVCalls             Netfront/Netback
> > > -P 1    9.9 gbit/s          4.53 gbit/s
> > > -P 2    17.4 gbit/s         5.57 gbit/s
> > > -P 4    24.36 gbit/s        5.34 gbit/s
> > >
> > > PVCalls is still significantly faster than Netfront/Netback.
> > This seems to be not a really fair comparison. And does not reflect
> > performance impact of the data copying itself.
> 
> Why it is not a fair comparison? Because the design is different or
> because of the settings? I am happy to adjust benchmarking settings to
> make the comparison fairer.
 
Actually it turns out that Netfront/Netback use another form of copy:
grant copies. So you are right that this comparison doesn't really
reflect copy vs. mapping performance.

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