Subject: bug#74855: 30.0.92; dired - slow copy across (wireless) LAN

From: Michael Albinus <[email-masked]>
Date: Thu, 19 Dec 2024 12:48:22 +0100

Stefan Kangas <[email-masked]> writes:

> Christopher Howard <[email-masked]> writes:
>
>> Hello. Recently I was using dired to transfer 600 files, with about
>> 2GB data total, across our LAN (one wi-fi hop involved). The source
>> was a local directory, and the target was an SSH host on the LAN. I
>> marked the files I wanted with dired-mark-files-regexp, and then
>> used dired-do-copy to send them to
>> "/ssh:<snip>@<snip>:/home/<snip>/<snip>". This took a really long
>> time. Actually, the copy was still going after about 15 hours
>> (overnight) though I could see it had not frozen up, but was still
>> moving files.
>>
>> Using scp directly, from Gnome console, I am seeing transfer rates
>> of about 2.5 MB/s over the same path. So, I'm wondering why the
>> large disparity. Could somebody explain further how Emacs goes about
>> moving the file data and where the bottleneck would be. Is there
>> room for improvement in this functionality?
>
> Michael, any comments?

Tramp's "ssh" method is not suited for this use case. It encodes the
local file with base64, and decodes it when it has been arrived on the
remote side.

For this given use case, Tramp's "scp" method is better suited. See the
discussion in the manual, (info "(tramp) Connection types") and (info
"(tramp) Frequently Asked Questions") , the entry "How to speed up TRAMP".

Best regards, Michael.