[Cake] faster scheduling, maybe

Benjamin Cronce bcronce at gmail.com
Mon Jun 6 18:34:12 EDT 2016

Preliminary benchmarks of new network APIs like netmap are showing 20mpps
 between guest and host for untrusted guests and 70mpps to trusted guests,
and scales near linearly with more cores. With that many pps per guest, why
not let the host do an AQM? High end service NICs support multiple virtual
devices where you can tell the NIC to evenly distribute bandwidth among the
virtual devices. It's already mostly a solved problem, just some people
reinventing the wheel. I know FreeBSD is currently looking at adding netmap
to connect the guest to the host so the guests can do line-rate 10Gb and
almost 40Gb.

On Mon, Jun 6, 2016 at 1:48 PM, David Lang <david at lang.hm> wrote:

> On Mon, 6 Jun 2016, Dave Taht wrote:
> http://info.iet.unipi.it/~luigi/papers/20160511-mysched-preprint.pdf
> I don't think so.
> They don't even try for fairness between flows, they are just looking at
> fairness between different VMs. they tell a VM that it has complete access
> to the NIC for a time, then give another VM complete access to the NIC. At
> best they put each VMs traffic into a different hardware queue in the NIC.
> This avoids all AQM decisions on the part of the host OS, because the
> packets never get to the host OS.
> The speed improvement is by bypassing the host OS and just having the VMs
> deliver packets directly to the NIC. This speeds things up, but at the cost
> of any coordination across VMs. Each VM can run fq_codel but it's much
> corser timeslicing between VMs.
> David Lang
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