refactor: remove iopoll from io_uring

[gabriele-0201]

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[gabriele-0201]

• opt: use io_uring single_issuer feature #808
• opt: increase io_uring ring capacity #807
• refactor: remove iopoll from io_uring #806 👈 (View in Graphite)
• master

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[deuszx]

Hey hey - just for the sake of my own learning: why did you remove this? Were there any issues with how this (not) worked?

[gabriele-0201]

As state in the docs:

This is only applicable for storage devices for now, and the storage device must be configured for polling
...
the nvme driver must be loaded with the poll_queues parameter set to the desired number of polling queues

What this means is that iopoll requires some really low-level configuration to work properly, it is not plug and play. If you try to cat /sys/module/nvme/parameters/poll_queues, you will probably get a zero, indicating that your nvme is not configured for polling. This is why it was removed for now, it was not providing any real benefit at some costs.