single stepping unbearably slow

Using gdb in the command line, i can get – i would guess – as far as 10 steps per second. Some steps take noticeably longer then others. Lldb seems even faster.

Starting from the same breakpoint in qtcreator, it takes more than 1 second for each step.
When the stepping cursor doesn’t instantly vanish and reappear after that time period in the next line, it does so after requesting next step twice in a row, probably waiting for the local variable population query to finish.

Sometimes it makes a difference if lldb or gdb is used.
In my test just now using lldb simply got stuck during the first single step. (And i have to select »Abort Debugging« twice to get it killed. Actually just now the red square to kill the program – which doesn’t work in this case, was still there, pressing it did nothing, and pressing ctrl+r segfaulted qtcreator)

This seems unacceptable to me.