Performance issue when using conditional request with ranges

[johaven]

On my laptop with a SSD disk, if i send file without ranges header, i can write a file with a speed of 500MB/s.
If i try to resume this file with ranges header, i obtain 40MB/s for the same CPU load.

Do you have the same behavior?

Environment:

• Python version: 3.8.13
• Werkzeug version: 2.2.0

[johaven]

It seems to be the RangeWrapper (wsgi.py) slowing down the sending of blocks, probably because it handles files like use cases and its iteration is subject to several conditions.
It is also possible that UWSGI does not handle this kind of wrapper very well.
If I manually reproduce the positioning of the range (seek) and send the chunks from this checkpoint in stream mode, I obtain the same read/write performance as the send_file function (conditional=False).

Why not let uWSGI manage this part? It looks like it can manage range-header (https://uwsgi-docs.readthedocs.io/en/latest/Changelog-1.9.6.html?highlight=honour%20range#preliminary-support-for-the-http-range-header).
The advantage is that we could implicitly use offload-threads instead of blocking a thread.
(unbit/uwsgi@03ceada)
A passthrough of this type might be interesting: 'honour-range' in uwsgi.opt ...

I know that uWSGI is not the only WSGI server and that it is not easy to integrate too many specificities, these are only ideas.