Why Disk IO type default isn't Simple pread/pwrite?

[qBittUser]

Is there any downside from using it, lack of tests or something else blocking from changing it as a next qBittorrent version recommended setting by default?

• Add "Simple pread/pwrite" disk IO type #21300

Reading this old pull request mentions that enabling it should help users who are still waiting for libtorrent v2 related qBittorrent issues to be resolved.

I couldn't find anyone mention issues with it and I couldn't notice any downsides enabling it myself.

Which is why I'm wondering if anyone knows why it it still isn't and why it shouldn't be enabled?

Note: when libtorrent v2.1.0 gets released, it will have new default Disk IO:

arvidn/libtorrent@fb4a525

So if you previously managed to change qBittorrent advanced options, then you will have to change back to Default or replace it with newer (potentially better) multithreaded pread/pwrite instead of using simple pread/pwrite or anything else.

[soredake]

Good news arvidn/libtorrent@fb4a525

[qBittUser]

Well no libtorrent release with it available yet as default and no comparison or tests mentioned by anyone, so no clue how much better is pread/pwrite compared to simple pread/pwrite or anything else.

Development qBittorrent builds currently do include libtorrent v2.1.0-rc1, but it doesn't have the new disk io as default for new users and has too much bugs compared to newer libtorrent.

So currently will have to wait for:

1. Official libtorrent pre-release v2.1.0-rc2 that includes new default Disk IO type: pread/write.
2. qBittorrent development builds in GitHub to include it.
3. New comparison tests by those users who had issues or saw downsides with using memory mapped or simple pread/pwrite.
4. New major libtorrent v2.1.0 release.
5. qBittorrent v5.3 or newer version to include it.
6. Wait for package managers to include it.
7. Include official qBittorrent installer with libtorrent v2.1.0 and have the new Disk IO option mentioned in qBittorrent news page.

Those who previously changed default qBittorrent disk io type will have to be reminded to reset their qBittorrent options (settings) or to manually pick pread/pwrite.

Would also be good to increase awareness and delay excess complaints by making a separate discussion thread that includes libtorrent v2 related issue reports and tests. Then it can help to keep track what still needs to be solved and might be better to delay getting official qBittorrent installers have libtorrent v2.1.0 as default until thorough tests are done. Otherwise might repeat what happened when v2.0+ was used by default.