A Fast, Growable Array with Stable Pointers in C

Re:A Fast, Growable Array with Stable Pointers in C by OptionOfT on Wednesday August 06, 2025 @10:59PM (#44820118)

One place I had issues was rapidly allocating space I needed temporarily but then discarding it.

The space I needed was too large to be added to the heap, so I used mmap. Because of the nature of the processing (mmap, process, yeet mmap) I put the system under a lot of pressure. Maintaining the set of mapped blocks and reusing them around fixed the issue.

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Re:A Fast, Growable Array with Stable Pointers in C by vlovich123 on Wednesday August 06, 2025 @11:01PM (#44820143)

Freeing memory to the OS or doing things like munmap involves a TLB shootdown which by definition is a performance bottleneck. Probably what you ended up experiencing.

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Re:A Fast, Growable Array with Stable Pointers in C by OptionOfT on Friday August 08, 2025 @10:56AM (#44837771)

Thanks for that. That was an interesting read!

I ended up in this situation like I end up in most, by just learning as I go.

With this I learned that the libc allocator has a max amount that it'll add to the heap, and how mmap works, and that doing frequent munmap is slow.

Now I learned why it is slow!

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