On 2019-02-11 6:44 a.m., Edward Cree wrote:
Hasnt been necessary thus far.
Is your end goal to match and count?
My end goal is to implement TC offload in some hw we're designing
here at Solarflare. So I'm trying to determine what hardware is
expected/required to do.
It might be possible to design our new hw so that we can attach a
counter to every action, if that's what TC wants.
It makes sense to have a counter on every action - even if it is
for debugging purposes. The two most basic actions are "drop" or
"accept". In TC speak the default action is "classid x:y" which
typically is to select a queue or give the flow some identity
(one should be able to use the same action on h/w ingress as well
to select a rx DMA ring for example, but that seems uncommon).
Note, your counters should also be shareable; example, count all
the drops in one counter across multiple flows as in the following
case where counter index 1 is used.
tc flower match foo action drop index 1
tc flower match bar action drop index 1
But since the
other vendors don't seem to do that, I wondered if there was a
reason, or if perhaps the counter resources (and PCI bw to read
them) could be saved if all those separate counters aren't really
needed.
Probably nobody has paid attention or asked as you did.
Will let the h/w folks speak for themselves. My understanding
based on experience is counters are cheap. Most modern NICs
and ASICs have a gazillion of them at their disposal.
Right now the design we are considering would only count
packets as-matched, i.e. before any edits. That's fine for encap
— you can calculate the bytes correction in SW — but not for decap
since in principle the length of the RXed outer headers could
vary (e.g. you might have IP options there).
ok, so not much in terms of other types of actions.
But for abstraction sake maybe use "flowid x:y" and have counters
associated with that. Or even make this optional and only attach
a counter if someone says "action ok" and allow them to specify
the counter index (assuming you architecture has an indexed table
of counters).
cheers,
jamal
