[dpdk-dev] Fwd: [dpdk-announce] DPDK Features for Q1 2015

[Jay Rolette <rolette@infiniteio.com>]

Tim,

Thanks for sharing this. If nothing else, I wanted to at least provide some
feedback on the parts that look useful to me for my applications/product.
Bits that make me interested in the release:



*> 2.0 (Q1 2015) DPDK Features:> Bifurcated Driver: With the Bifurcated
Driver, the kernel will retain direct control of the NIC, and will assign
specific queue pairs to DPDK. Configuration of the NIC is controlled by the
kernel via ethtool.*

Having NIC configuration, port stats, etc. available via the normal Linux
tools is very helpful - particularly on new products just getting started
with DPDK.


*> Packet Reordering: Assign a sequence number to packets on Rx, and then
provide the ability to reorder on Tx to preserve the original order.*

This could be extremely useful but it depends on where it goes. The current
design being discussed seems fundamentally flawed to me. See the thread on
the RFC for details.


*> Packet Distributor (phase 2): Implement the following enhancements to
the Packet Distributor that was originally delivered in the DPDK 1.7
release: performance improvements; the ability for packets from a flow to
be processed by multiple worker cores in parallel and then reordered on Tx
using the Packet Reordering feature; the ability to have multiple
Distributors which share Worker cores.*

TBD on this for me. The 1.0 version of our product is based on DPDK 1.6 and
I haven't had a chance to look at what is happening with Packet Distributor
yet. An area of potential interest at least.


*> Cuckoo Hash: A new hash algorithm was implemented as part of the Cuckoo
Switch project (see http://www.cs.cmu.edu/~dongz/papers/cuckooswitch.pdf
<http://www.cs.cmu.edu/~dongz/papers/cuckooswitch.pdf>), and shows some
promising performance results. This needs to be modified to make it more
generic, and then incorporated into DPDK.*

More performance == creamy goodness, especially if it is in the plumbing
and doesn't require significant app changes.


*> Interrupt mode for PMD: Allow DPDK process to transition to interrupt
mode when load is low so that other processes can run, or else power can be
saved. This will increase latency/jitter.*

Yes! I don't care about power savings, but I do care about giving a good
product impression in the lab during evals without having to sacrifice
overall system performance when under load. Hybrid drivers that use
interrupts when load is low and poll-mode when loaded are ideal, IMO.

It seems an odd thing, but during lab testing, it is normal for customers
to fire the box up and just start running pings or some other low volume
traffic through the box. If the PMDs are configured to batch in sizes
optimal for best performance under load, the system can look *really* bad
in these initial tests. We go through a fair bit of gymnastics right now to
work around this without just giving up on batching in the PMDs.


*> DPDK Headroom: Provide a mechanism to indicate how much headroom (spare
capacity) exists in a DPDK process.*

Very helpful in the field. Anything that helps customers understand how
much headroom is left on their box before they need to take action is a
huge win. CPU utilization is a bad indicator, especially with a PMD
architecture.

Hope this type of feedback is helpful.

Regards,
Jay