--info=progress2 flag displays wrong transfer rates

[Anish Shankar]

Hi,
I'm a bit new to rsync, and I recently learnt about the --info=progress2
flag to display complete transfer progress. However while transferring I
encountered some unusually large transfer rates being displayed repeatedly.
I used "rsync -av --info=progress2" to transfer a folder with several large
files. Every time a new file was started , the initial transfer rate was
unusually high (500~ MB/s instead of 30-40) and correspondingly showed an
impossibly small ETA.

It appeared as if rsync was calculating the entire file as transferred in
an instant (resulting in a very high rate displayed), followed by no change
in transfer amount resulting in the speed decaying, reaching actual speed
only when the file actually completes transferring. Although the file-wise
transfer rates displayed after completion are correct, the current file's
speed is always higher than what it should be.

A little bit of digging into the code showed that this was exactly what was
happening. Can someone tell if this was the expected behaviour or this is a
bug that can be fixed? I made a quick patch to try to reverse calculate the
correct transfer rate based on the offsets (find patch attached), which
seems to work correctly for my use-cases.

Regards
Anish
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