Red Hat Bugzilla – Bug 346
Screen takes a long time to switch over telnet
Last modified: 2008-05-01 11:37:48 EDT
With the introduction of redhat 5.1, screen shows a delay of up to 5 seconds, depending on screen content, to switch between virtual consoles over any kind of network conenction (telnet/ssh), in 5.0 and prior the switchover occured almost immediately. As not only the screen RPM's but also custom complied versions are affected, i am suspecting a problem in the curses libraries.
Tried this in the lab, and things worked with full-screen ps displays. Delay of less than a second. By any chance are you seeing network delays that are resulting in the lag, or is there some other display that we should try this with?
Red Hat Linux release 5.1 (Manhattan) Linux tesla.femu.rwth-aachen.de 2.0.35 #7 Tue Sep 8 13:53:25 CEST 1998 i686 unknown 10:12am up 57 days, 23:32, 2 users, load average: 0.00, 0.00, 0.00 Screen version 3.07.04 (FAU) 23-Jun-97 Using ZOC V3.10 in both Telnet and SSH mode, terminal emulation VT220 in 164x54 character resolution, i do the following: screen # invoke screen man ls # fill the first screen with a man page ctrl+a c # create second screen man cp # fill the second screen with a man page ctrl+a 0 # switch back to first screen The time between the 0 and the actual switchover is 9 seconds. Same if i switch back to screen 1 with ctrl+a 1. If i invoke a 3rd screen and leave it empty, the switchover to that EMPTY screen takes about 1,5 seconds, the switch back to a screen with content (man pages, etc) the same 9 seconds mentioned above. Up till and including redhat 5.0 this was working instantaneously (p.s. the host machine is a dual PII-400, 512 MB Ram, switched 100baseT network. The client machine a single PII-350 with 128 MB ram running windows95OSR2 and ZOC Terminal program (www.emtec.com). Network utilisation at 3% during the test. The behaviour can be reproduced on all other linux hosts running redhat here, whether it be alpha or intel version (no Sparc, sorry), as soon as i try it on a 5.0 distribution switchover times are typically less than 0,5 seconds.
In test lab, telneted in from Win98 terminal to Linux host and did see longer than usual delay in screen switches. Not able to see same delays telneted in from Linux workstations. Tried with 4.2 system in lab and sure enough switches were quicker!
From Alan Cox during Red Hat 5.2beta2: screen is still broken. Set the terminal type to vt100 (or better yet get a real vt100) and try switching screens or doing things like an ls -lR / - it crawls. This is a known problem with screen and ncurses4.
*** Bug 346 has been marked as a duplicate of this bug. *** > > The system is an upgrade from RedHat 5.0 and under 5.0, screen had > extremely quick response times in doing a switch from screen to screen as > well as doing something as simple as doing an ls in the /etc directory. > > Under RedHat 5.2 however, fliping from one screen to the next takes at > least 3-4 seconds, and doing a directory listing under /etc (ls) results > in the first line appearing immediately, then the rest of the listing > appearing 2-3 seconds later. > > Is this a problem with the machine, OS, or should I recompile screen. It's a ncurses problem. Our new version contains a workaround. You can get it from: ftp://ftp.uni-erlangen.de/pub/utilities/screen/screen-3.7.6. tar.gz ------- Additional Comments From ayn2@cornell.edu 01/15/99 23:29 ------- This is a duplicate of #346 ------- Additional Comments From mchoi@ap.net.hk 01/16/99 00:20 ------- Sorry, first time posting on bigzilla, didn't see the previous post. I compiled the new screen version(3.7.6) and all problems are gone. The Linux Server machine is only a pentium 166 with 128MB RAM and a 6.4 GB IDE Drive.
Screen 3.76 is part of Raw Hide. Get the source rpm from there and recompile if you want to correct this problem.
The source rpm in Raw Hide is screen-3.7.6-1.src.rpm (not 3.76). Sorry for the confusion.