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io_uring is faster than mmap

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283 points ghuntley | 2 comments | 04 Sep 25 22:01 UTC | HN request time: 0.57s | source
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modeless ◴[05 Sep 25 03:25 UTC] No.45134728[source]▶
Wait, PCIe bandwidth is higher than memory bandwidth now? That's bonkers, when did that happen? I haven't been keeping up.

Just looked at the i9-14900k and I guess it's true, but only if you add all the PCIe lanes together. I'm sure there are other chips where it's even more true. Crazy!

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DiabloD3 ◴[05 Sep 25 03:41 UTC] No.45134790[source]▶
"No."

DDR5-8000 is 64GB/s per channel. Desktop CPUs have two channels. PCI-E 5.0 in x16 is 64GB/s. Desktops have one x16.

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1. modeless ◴[05 Sep 25 03:48 UTC] No.45134821[source]▶
Hmm, Intel specs the max memory bandwidth as 89.6 GB/s. DDR5-8000 would be out of spec. But I guess it's pretty common to run higher specced memory, while you can't overclock PCIe (AFAIK?). Even so I guess my math was wrong, it doesn't quite add up to more than memory bandwidth. But it's pretty darn close!
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2. DiabloD3 ◴[05 Sep 25 04:52 UTC] No.45135087[source]▶
There is a difference between recommended and max achievable.

Zen 5 can hit that (and that's what I run), and Arrow Lake can also.

The recommended from AMD on Zen 4 and 5 is 6000 (or 48x2), for Arrow Lake is 6400 (or 51.2x2); both of them continue increase in performance up to 8000, both of them have extreme trouble going past 8000 and getting a stable machine.