Comment # 14 on bug 99130 from Dorota Czaplejewicz

# cat /proc/consoles
tty0                 -WU (EC p  )    4:1

Upon further digging, the slow stack *seems* like this (may be wrong, the
tracing tool is less useful with huge numbers of calls):

console_unlock()
 call_console_drivers.isra.0.constprop.15()
  vt_console_print()
   lf()
    scrup()
     fbcon_scroll()
      fbcon_cursor()
       fbcon_redraw.isra.17()

Inside of this, the delay is split up among many shorter calls, most time
occupied by fbcon_putcs -> bit_putcs -> cfb_imageblit.