On Mon, 13 Aug 2018, Jan Ehrhardt via curl-library wrote:

> Daniel Stenberg (Thu, 9 Aug 2018 16:55:38 +0200 (CEST)):
> -#define UPLOAD_BUFSIZE CURL_MAX_WRITE_SIZE
> +#define UPLOAD_BUFSIZE (512*1024)
>
> @Daniel Stenberg: is there a reason that is stopping you from changing this
> in curl?

Yes. (Pretty much explained already in the TODO:
https://curl.haxx.se/docs/todo.html#Modified_buffer_size_approach)

1. This buffer is allocated as part of the regular easy handle and increasing
that allocation this much in one go I fear will cause problems to some
existing applications out there. Especially those doing a huge amount of
parallel transfers.

2. There's basically only SFTP that needs this huge buffer so it seems
wasteful to always use such a large buffer if it isn't necessary. I would like
to see it conditionally enlarged if SFTP is indeed used.

3. I think it might be a good idea to let the application control the SFTP
size, so that the 1,000 parallel transfer applications can use a smaller
buffer and the single connection apps can use a larger.

Besides all that, it would also be interesting to work out what an "ideal"
size might be. Is 512KB large enough? Is 256KB enough for 99% of the cases?
Would 1MB help in the extremely high speed high latency cases?

Would it be sensible to attempt to detect the situation and dynamicly grow the
size if deemed fine?

-- 
  / daniel.haxx.se
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