[dspillett]

> woefully unparallelisable

It certainly doesn't use multiple cores for a single connection, though I've never tested (or reviewed the code) to see if it does manage to spread the computational load of multiple connections over more CPU resource.

I've not read the above linked article in detail (no time ATM) but there seems to be mention of offloading AES calculations to compatible hardware, so the bottleneck would appear to be CPU use.

[cbhl]

Does using multiple cores on a single NIC actually speed up a network connection? If you're doing gigabit with 1500 byte packets, you get 12 ms to encrypt and process each packet -- I'd expect any cross-CPU synchronization to easily blow through that.

[05]

If the bottleneck is encryption speed, then you can definitely improve perf by spreading packets across the cores. Inter-core synch isn’t that expensive, and 12us is 24000 cycles on a 2GHz CPU. cmpxchg costs ~20 cycles (https://stackoverflow.com/questions/4187914/average-latency-...).

PS. And you don’t need to submit/receive packets to NIC one by one, either; those things support DMA scatter/gather.

[cbhl]

That's a really helpful response; thanks!