Re: Xen network domain performance for 10Gb NIC

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Apr 28, 2020 at 05:23:55AM +0000, tosher 1 wrote:
> > Driver domains with passthrough devices need to perform IOMMU
> operations in order to add/remove page table entries when doing grant
> maps (ie: IOMMU TLB flushes), while dom0 doesn't need to because it
> has the whole RAM identity mapped in the IOMMU tables. Depending on
> how fast your IOMMU is and what capabilities it has doing such
> operations can introduce a significant amount of overhead.
> 
> It makes sense to me. Do you know, in general, how to measure IOMMU 
> performance, and what features/properties of IOMMU can contribute to getting 
> a better network throughput? Please let me know. 

Hm, not really. You would have to modify Xen and/or the Linux kernel
in order to time the IOMMU or the grant map operations in order to get
an idea.

Do you get the expected performance from the driver domain when not
using it as a backend? Ie: running the iperf benchmarks directly on
the driver domain and not on the guest.

Roger.