Slow display in Teraterm (2019-09-10 21:38 by loobo #83548)
I love Teraterm and use it as my primary terminal emulator when ssh'ing to servers... but there is one thing that really annoyes me... It gets slow when scrolling though a lot of text. For example, listing a few directories may produce quite a few lines of text and it takes a LOT longer to show all those lines of text in Teraterm than it does in, for example Putty.
Running "ls -laR" on /etc takes less than 1 sec if I use Putty. We are takling about perhaps a tenth of a second...
If I do the same in Teraterm, text keeps scrolling on screen for like four and a half seconds...
If I time the command with "time" and run "time ls -laR" the final output when running in Putty is:
...and in Teraterm:
That suggests that the command actually finishes on the server quite fast (even though a slower when Teraterm is used) but then the output is buffered and showed in Teraterm quite slow.
Also, hitting Ctrl-C doesn't abort the listing. I think it's sent to the server but as the server is already done, there's nothing to abort :-/ This can be really annoying if you by misstake lists a file with say 30000 lines... You can't abort that listing. I'm pretty sure, though, that a Ctrl-C IS indeed sent to the server at the moment it is pressed. If the execution of a command, that produces a lot of output, takes, for example, 10 seconds to run on the server and you hit Ctrl-C after 5 seconds, the executions stops on the server but the output already produced keeps getting scrolled though by Teraterm... which may keep scolling text for a minute or even longer...
All this gets even way worse when using tmux.
A nice thing with tmux is that you can connect with both Teraterm and Putty to the same system and attach to the same tmux-session. That gives you both input and output to in both terminal-windows. Using this to show the difference between Teraterm and Putty is perfect. I know tmux adds latency itself as it has to buffer and redraw, but the same added latency would be appearent in both teminals. This added latency is particular appearent when having a vertical split, not so much with a horizontal split, though.
Having both terminals side-by-side and running "ls -laR" (in /etc) in the tmux-session with no splits shows about the same times to complete as running the command outside of tmux. Having a vertical split in tmux is a total different story. In the Putty-window the listing takes about 3.2 seconds to complete but it takes a total of 36.8 seconds to complete in the Teraterm-window... This is where it starts to get really anoying... As I also timed the command execution I can say it takes somewhere between 0,5 an 1 second to complete (multiple runs)... and pressing Ctrl-C after a few seconds doesn't help as the command execution is already completed on the server.