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Comment by qaq | Hacker News Reader

Unless you are running on NUMA box does not look like this will affect you much.

Isn't NUMA how multi-core CPUs work still?

At least the AMD Bulldozer architecture diagram on the Wikipedia NUMA page shows this, both within a socket and between sockets:

https://en.wikipedia.org/wiki/Non-uniform_memory_access#/med...

Is the same true for Intel chips? (The Wikipedia page mentions the Intel E8870 memory controller, but not whether newer chips use similar set-ups)

> Isn't NUMA how multi-core CPUs work still?

if you have > 1 socket, then yes, otherwise no.

Edit: added verb

These days, yeah, that's definitely the case. A few generations back there were a couple of multi-socket-single-memory-domain designs.

> A few generations back there were a couple of multi-socket-single-memory-domain designs.

Core2Quad/Duo based Xeons, P4s, Athlon MP, etc

I thought the Core2 chips were actually multiple single-core processors on a single slab, which would make that true of all Core2 machines (not just Xeons). I was pretty deep in Nehalem details when it first came out and was under the impression that microarchitecture was Intel's first true multi-core chip (as in, the cores were actually integrated on the die). Could be wrong, though, since I never delved into the Core2 architecture.

>I thought the Core2 chips were actually multiple single-core processors on a single slab, which would make that true of all Core2 machines (not just Xeons)

Correct.

To my understanding, multi core on a single package (CPU) is much simpler to schedule. There are performance penalties if you schedule work on a package that has to access memory that is not directly connected. A NUMA-aware scheduler should not make this mistake.

Looks like you are right Intel QuickPath Interconnect is similar to what AMD was doing with HT.

The computing world is quickly heading towards two different style targets: (1) ones that have a single memory domain inside a smartphone or tablet that infrequently execute CPU-bound or memory-bound tasks and (2) ones that have a NUMA architecture inside a server that often execute CPU-bound/memory-bound tasks.

False. Cache misses are expensive. Unnecessary thread sleeps and context switches are expensive.

So, you mean, pretty much every server produced in the last ~8 years?

Not much impact to desktop users, but a huge impact for servers.

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