Into.the.Void.

I just noticed a somewhat strange behaviour of xterm. When savelines option is set to a high number, say above 10000, the output of xterm is REALLY REALY slow.

Check the following examples on maximized xterm windows:
File: .xsession-errors 200074 (200kbytes)

% wc -l .xsession-errors
4103 .xsession-errors
% xterm -v
XTerm(218)
% mrxvt --help
Mrxvt v0.5.1
Options: XPM,Jpeg,PNG,transparent,fade,tint,textshadow,utmp,menubar,XIM,multichar_languages,scrollbars=rxvt+NeXT+xterm+sgi+plain,
xft,Greek,frills,linespace,24bit,selectionscrolling,256colour,cursorBlink,pointerBlank,session management,Resources


XTerm*saveLines: 500
% time cat .xsession-errors
cat .xsession-errors 0.00s user 0.00s system 0% cpu 0.933 total


XTerm*saveLines: 1000
% time cat .xsession-errors
cat .xsession-errors 0.00s user 0.00s system 0% cpu 1.029 total


XTerm*saveLines: 2500
% time cat .xsession-errors
cat .xsession-errors 0.00s user 0.01s system 0% cpu 1.286 total


XTerm*saveLines: 5000
% time cat .xsession-errors
cat .xsession-errors 0.00s user 0.00s system 0% cpu 1.382 total


XTerm*saveLines: 10000
% time cat .xsession-errors
cat .xsession-errors 0.00s user 0.00s system 0% cpu 1.969 total


XTerm*saveLines: 11000
% time cat .xsession-errors
cat .xsession-errors 0.00s user 0.00s system 0% cpu 3.038 total


XTerm*saveLines: 20000
% time cat .xsession-errors
cat .xsession-errors 0.00s user 0.00s system 0% cpu 8.341 total


XTerm*saveLines: 32767
% time cat .xsession-errors
cat .xsession-errors 0.00s user 0.01s system 0% cpu 12.798 total


On my faithfull mrxvt with 32767 buffer lines this gives me:
mrxvt*saveLines: 32767
% time cat .xsession-errors
cat .xsession-errors 0.00s user 0.01s system 0% cpu 1.494 total


I hope you notice the difference…

“bug” or “feature” ? who knows…

Filed by kargig at 02:34 under Linux
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