`io_uring_queue_init_mem` is unusable from Python

[meshya]

Current wrapper marked as not tested, while it can not called from Python:

1. Param class (class.zig ) has no __new__ and _io_uring_params will not initialize.
2. A pointer to huge page ( which needed to supply as buf ) cannot created in python. A bytesarray does not satisfy this.
3. No strategy to free this buffer in io_uring_queue_exit or Ring.__del__.

What to do?

I think we can add a param to Ring which holds pointer to buffer. and initialize buffer in io_uring_queue_init_mem wrapper.

[meshya]

I'd be happy to take this on and open a PR with a fix if that sounds good.

[YoSTEALTH]

I haven't had the time to fully test all the code written. If you want to take a crack at it you are welcome to do so. It should be easy to create __new__ and __del__ in Param (look at Ring). Also all the function in uring.zig that use Param should work as well with new changes. Of course tests.

When you say "huge page" are you talking about IORING_SETUP_SQE128, IORING_SETUP_CQE32?

The goal with this library structure is to be as close to C Liburing functions and usage as much as possible. If you create too many custom class/function it can get out of hand to maintain and usage, for that other higher level library would be better.

This library is Free, Public Domain (CC0) if you don't mind submitting PR to that.

[meshya]

Thanks!

By "huge page" I meant the man-page quote for io_uring_queue_init_mem, not IORING_SETUP_SQE128/CQE32

The buffer passed to io_uring_queue_init_mem(3) must be page size aligned on the
host, and must already be zeroed. Typically, the caller should allocate a huge
page and pass that in to io_uring_queue_init_mem(3). Pages allocated by mmap are
already zeroed.

So rather than allocating inside the wrapper, I'll take the buffer as an argument and let the caller pass Python's stdlib mmap.mmap — just like C.
Only new code is Param.__new__/__del__.

PR this week.