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io_uring is faster than mmap

(www.bitflux.ai)
283 points ghuntley | 12 comments | 04 Sep 25 22:01 UTC | HN request time: 0.2s | source | bottom
1. hsn915 ◴[04 Sep 25 23:56 UTC] No.45133595[source]▶
Shouldn't this be "io_uring is faster than mmap"?

I guess that would not get much engagement though!

That said, cool write up and experiment.

replies(3): >>45133612 #>>45134589 #>>45136289 #
2. jared_hulbert ◴[05 Sep 25 00:00 UTC] No.45133612[source]▶
Lol. Thanks.
replies(1): >>45135343 #
3. dang ◴[05 Sep 25 02:58 UTC] No.45134589[source]▶
Let's use that. Since HN's guidelines say ""Please use the original title, unless it is misleading or linkbait", that "unless" clause seems to kick in here, so I've changed the title above. Thanks!

If anyone can suggest a better title (i.e. more accurate and neutral) we can change it again.

4. MaxikCZ ◴[05 Sep 25 05:48 UTC] No.45135343[source]▶
Its not even about clickbait for me, but I really dont want to go parse an article to figure out what is meant by "Memory is slow, Disk is fast". You want "clickbait" to make people click and think, we want descriptive tittles to know what the article is about before we read it. That used to be original purpose of tittles, we like it that way.

Its like as if youd label your food product "you wont believe this", and forced customers to figure what it is from ingredients list.

replies(2): >>45136268 #>>45141749 #
5. robertlagrant ◴[05 Sep 25 08:26 UTC] No.45136268{3}[source]▶
> Its like as if youd label your food product "you wont believe this", and forced customers to figure what it is from ingredients list.

Indeed[0].

[0] https://en.wikipedia.org/wiki/I_Can't_Believe_It's_Not_Butte...!

replies(1): >>45143616 #
6. nine_k ◴[05 Sep 25 08:29 UTC] No.45136289[source]▶
No. "io_uring faster than mmap" is sort of a truism: sequential page faults are slower than carefully orchestrated async I/O. The point of the article is that reading directly from a PCIe device, such as an NVMe flash, can actually be faster than caching things in RAM first.
replies(1): >>45140950 #
7. wmf ◴[05 Sep 25 17:11 UTC] No.45140950[source]▶
reading directly from a PCIe device, such as an NVMe flash, can actually be faster than caching things in RAM first.

That's not true though, because the PCIe device DMAs into RAM anyway.

replies(1): >>45145587 #
8. jared_hulbert ◴[05 Sep 25 18:14 UTC] No.45141749{3}[source]▶
I get that. But I do actually show a scenario where accessing data from memory using a very standard mechanism IS slower than a newer but equally standard way of accessing data from an NVMe drive.

"Accessing memory is slower in some circumstances than direct disk access"

9. MaxikCZ ◴[05 Sep 25 21:06 UTC] No.45143616{4}[source]▶
Oh god..
10. nine_k ◴[06 Sep 25 01:02 UTC] No.45145587{3}[source]▶
No, it can DMA straight into L3 cache, as mentioned in the article.

See https://www.intel.com/content/www/us/en/io/data-direct-i-o-t...

replies(1): >>45146256 #
11. wmf ◴[06 Sep 25 03:01 UTC] No.45146256{4}[source]▶
Your server doesn't have DDIO turned on though.
replies(1): >>45146577 #
12. nine_k ◴[06 Sep 25 04:19 UTC] No.45146577{5}[source]▶
Not mine, but fair!