On Tue, 16 Jul 2019, Taras Kushnir via curl-library wrote:
The reason why I’m asking this is the following: I got reports from users
that my app “uploads very slowly” so I started this investigation. Default
upload code heavily (like x3-x4 on my machine) underperforms FileZilla
upload and commandline “ftp" utility even for 1 file to 1 server (that
eliminates my theoretical threading implementation bugs etc.).
I've not seen/heard this before.
What libcurl version on what platform? Have you seen this "slowness" on more
than one version/platform?
Is this against any or particular servers?
When you do these "slow" uploads, what's the RTT to server, roughly?
If, when doing FTP upload for 1 file for 1 server, I’m setting
CURLOPT_UPLOAD_BUFFERSIZE, upload speed increases for some users of my app
to “almost satisfactory”.
When you set it to what value? What does "almost satisfactory" mean in terms
how it compares to other tools then?
However, same setting cause FTP response timeouts on _every_ transfer for
other users (who, if I understand correctly, have much lower bandwidth).
That sounds really weird and would rather imply a (separate) bug.
On my machine (macbook pro 2015) and bandwidth I feel almost no difference
when playing with UPLOAD_BUFFERSIZE.
In my own tests, UPLOAD_BUFFERSIZE mostly make a difference when you have near
infinite bandwidth, like uploading on localhost. (And when when using SFTP,
but I assume we're not talking about that here.)
Therefore comes a question: is there any idiomatic way of using libcurl for
such cases that will solve upload speed issues for users both with big and
small bandwidth?
Increasing buffer size shouldn't hurt transfer speeds for any users!
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