On 15-12-08 02:33 AM, John Fastabend wrote:
On 15-12-02 04:15 PM, Tom Herbert wrote:
Just keying off the last statement there...
I think BPF programs are going to be hard to translate into hardware
for most devices. The problem is the BPF programs in general lack
structure. A parse graph would be much more friendly for hardware or
at minimum the BPF program would need to be a some sort of
well-structured program so a driver could turn that into a parse graph.
This might be relevant:
http://richard.systems/research/pdf/IEEE_HPSR_BPF_OPENFLOW.pdf
Thanks Tom interesting read but they seem to argue for a BPF engine in
hardware which I'm still not convinced is necessary and the numbers
provided are for a 1Gbps link where 10Gpbs/100Gbps+ would be more
valuable.
I am still leaning towards a fully programmable parse graph and a set
of basic actions push/pop/set/fwd/etc. This would be useful for other
features not just checksum offloads. I guess it doesn't necessarily
exclude also having 1s complement logic though.
;-> I feel a little vindicated with this discussion.
Of course you can implement hardware using BPF! I think there is an
opportunity for someone to build such hardware, if one is not in
progress of being built yet.
A BPF hardware implementation is just a very different approach;
instead of it being a series of TCAM table hardware implementation
(and/or other types of implementation which use DRAM etc), it becomes
CPU instructions. Surely one can cast the EBPF bytecode into an ASIC.
My disagreement with Tom is laying a stake that this is how hardware
features are to be exposed.
My disagreement with you is laying a stake in the ground that hardware
oughta be implemented using a series of Tubes^WTCAMS.
When i build a graphics card the API is not how the internal
implementation works. Everbody conforms to the same driver APIs.
Likewise, we have Linux APIs - and switchdev
is the right direction. Write your driver to switchdev interfaces.
Let a thousand flowers bloom.
BTW: It is bordering on the abstraction-ridiculous when I see the
P4 claims to use ebpf and then somehow translate to use
classifier/actions.
cheers,
jamal
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