port-amd64/59361: paging up in less(1) under qemu vga console is slow

[campbell+netbsd%mumble.net@localhost]

>Number:         59361
>Category:       port-amd64
>Synopsis:       paging up in less(1) under qemu vga console is slow
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-amd64-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Apr 26 16:35:00 +0000 2025
>Originator:     Taylor R Campbell
>Release:        current
>Organization:
The Slow386BSD Emulation
>Environment:
>Description:
Paging _down_ in less(1) under qemu vga console is reasonably quick.  Not instantaneous -- I still see a flicker sometimes -- but quick enough.

Paging _up_ in less(1) under qemu vga console is excruciatingly slow, takes multiple seconds to go a single page in a 25x80 display.
>How-To-Repeat:
1. run NetBSD/amd64 under qemu-system-x86_64
2. dmesg | less, or whatever
3. hit SPC to page down, hit b to page up
>Fix:
Yes, please!

Someone should alert the resident graphics expert.