X11 forwarding extremely slow (unusable) after Cygwin upgrade on Dec 23rd

[Ian Puleston]

Hi,

I have a Cygwin installation on a Windows 10 PC, on which I use X-Windows to access a Linux development/build server. All has been working great for a long time, until I rand a Cygwin upgrade on December 23rd, and after that X11 has become pretty much unusable. I normally launch the terminator terminal emulator locally under X, in that I "ssh -Y" to the Linux machine, and then on there I use a number of GUI apps, mainly SlickEdit and BeyondCompare, which run remotely via X11 forwarding to display in windows on my local Windows PC. But since this Cygwin upgrade all of those remote X11 apps are now extremely slow to respond to anything - about 10 to 20 seconds to action any key press or mouse click.

The two machines are on the same Gig-Ethernet LAN segment so there are no latency issues there (ping response time <1mS).

To take any possible problems with those components out of the picture, I tried instead launching xterm under X11 locally, and from it launching Firefox after ssh to the Linux machine, and again I see the same symptoms with that - trying to type into Firefox's address bar takes about 10 seconds per letter.

I had previously updated my Cygwin installation on March 3rd 2019, so this problem has come in sometime between then and now. I've just spent a very long day and a half rolling back the changes as much as I could (by hacking the setup.ini and re-installing previous versions from the local download cache) and eventually managed to get a working hybrid with enough packages rolled back to make the difference, and now X11 is working fine again.

I also tried a new clean install of the latest Cygwin, after deleting my .XWinrc and removing all but the bare minimum from .startxwinrc, and do see the problem with that too.

Is this any known problem? I couldn't find anything obvious in the email archives.

Ian

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