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io_uring is faster than mmap

(www.bitflux.ai)
283 points ghuntley | 1 comments | 04 Sep 25 22:01 UTC | HN request time: 0.216s | source
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bawolff ◴[05 Sep 25 00:26 UTC] No.45133765[source]▶
Shouldn't you also compare to mmap with huge page option? My understanding is its presicely meant for this circumstance. I don't think its a fair comparison without it.

Respectfully, the title feels a little clickbaity to me. Both methods are still ultimately reading out of memory, they are just using different i/o methods.

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jared_hulbert ◴[05 Sep 25 01:06 UTC] No.45134007[source]▶
The original blog post title is intentionally clickbaity. You know, to bait people into clicking. Also I do want to challenge people to really think here.

Seeing if the cached file data can be accessed quickly is the point of the experiment. I can't get mmap() to open a file with huge pages.

void* buffer = mmap(NULL, size_bytes, PROT_READ, (MAP_HUGETLB | MAP_HUGE_1GB), fd, 0); doesn't work.

You can can see my code here https://github.com/bitflux-ai/blog_notes. Any ideas?

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1. jandrewrogers ◴[05 Sep 25 02:23 UTC] No.45134410[source]▶
Read the man pages, there are restrictions on using the huge page option with mmap() that mean it won’t do what you might intuit it will in many cases. Getting reliable huge page mappings is a bit fussy on Linux. It is easier to control in a direct I/O context.