[Cake] Using cake to shape 1000’s of users.

Dave Taht dave.taht at gmail.com
Sat Jul 28 12:36:47 EDT 2018

On Sat, Jul 28, 2018 at 9:11 AM Jonathan Morton <chromatix99 at gmail.com> wrote:
> > On 28 Jul, 2018, at 6:51 pm, Dave Taht <dave.taht at gmail.com> wrote:
> >
> > That's also pretty low end. On the high end nowadays there's stuff like this:
> >
> > https://www.amazon.com/Intel-Xeon-E5-2698-Hexadeca-core-Processor/dp/B00PDD1QES
> Intel is no longer high-end for x86 CPUs.  Not all of the market has realised that yet, but it's true.
> Look at Threadripper 2 which scales up to 32 cores, 64 threads in a single socket at HEDT prices, and EPYC which just goes bonkers in terms of I/O capabilities and still costs less than its nearest Intel competitor.  None of which has any serious concerns with the recent series of Meltdown/Spectre speculation bugs, unlike Intel.

That haunts me.

> AMD is moving to a 7nm silicon process which apparently works pretty well already, and is theoretically on par with Intel's 10nm process which they still haven't got working reliably after how many years of delays now?  And they're already beating Intel over the head with a 14nm process which is theoretically *inferior* to Intel's 14nm process, which they'll be stuck with in practice for *at least* the next year even by their own wildly optimistic latest estimates.
> The only place Intel temporarily holds a real advantage is in maximum single-threaded turbo clock speed.

Which is important. Myself, I dream of cpus that can context switch in
5 cycles like the mill. For I/O
heavy workloads it's context switching that is rather important. There
is also a new generation of
multi-core arms, some with devkits like netronome's and caviums.

My take on all this would be to try and benchmark some stuff. Some
other bottleneck will surface. We have one benchmark of 4000 users at
4GigE to work with at the moment.

I've long pointed out that one big reason for GRO/GSO is the cost of a
routing lookup. mellonox, I think(?), *finally* added TCAM support to
their cards in  a patch that just went by on the netdev mailing list.

> This is relevant to a shrinking minority of users these days.  AMD's next CPUs are supposed to make that wholly irrelevant with a significant further jump in IPC - because they were designed to compete with 10nm Intel CPUs that Intel now looks very unlikely to be capable of manufacturing.

One huge advantage intel had was dma into cache. Still?

> And is this relevant to "Super Mega Turbo Cake Edition XLRi"?

Hahahaha. That comes up with 7000 hits for a hair dryer.


> Well, one of the nice things about having lots of users is that you can statistically multiplex them across multiple hardware queues more easily.  Each subscriber's traffic can sanely end up on the same queue each time, and each queue can have a separate "Super Cake" instance allocated an even division of the total backhaul bandwidth, and in theory each of *those* can run on its own CPU core.  Instant throughput boost.

I'd believe it when I benchmarked it, not before.

>  - Jonathan Morton


Dave Täht
CEO, TekLibre, LLC
Tel: 1-669-226-2619

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