Anyone knows why Mayastor io-engine is using magic number 512 to check if there are enough huge pages?

[cmontemuino]

This is the specific line used for checking if there are enough huge pages:

    if nr_pages + nr_1g_pages * 512 < PAGES_NEEDED {
    # ...

https://github.com/openebs/mayastor/blob/v2.7.0/io-engine/src/bin/io-engine.rs#L42

According Mayastor's installation guide, it requires a minimum of 2GiB of 2MiB-sized pages.

If my math is correct, the requirement is to have 1024 pages, which is exactly what's configured in:

const PAGES_NEEDED: u32 = 1024;

https://github.com/openebs/mayastor/blob/v2.7.0/io-engine/src/bin/io-engine.rs#L42

I cannot figure out expression nr_1g_pages * 512. 512 pages with size 1GiB is 512GiB, right?

Am I missing something?

[tiagolobocastro]

Probably not the clearest piece of code.
1page of 1GiB pages is equivalent to 512 pages of 2MiB pages

[cmontemuino]

Got it!!! Somehow I was mixing page sizes. We're always talking about of 2MiB page size.

Perhaps a comment would help, but still the code is clear enough.

Thanks!!