why Qt4 is so slower than Qt3 ?

i have a example that updates 30 QLineEdit's text every 1s in a QTimer's slot.
the example used by Qt4 is much slower than that used by Qt3. cpu useage is 40% (Qt4) than 20%(Qt3), my target machine is samsung 2410.

the same question was asked in Qt Centre too.
http://www.qtcentre.org/forum/f-qt-p...gets-4577.html

can anybody give me some advise?thank you very much!

Use a table view with one open editor at time instead of a table of line editors. Nobody edits multiple editors same time anyway.