[Bug 281252] Framebuffer writes are very slow on BeagleBone Black

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=281252

            Bug ID: 281252
           Summary: Framebuffer writes are very slow on BeagleBone Black
           Product: Base System
           Version: 13.4-STABLE
          Hardware: arm
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: arm
          Assignee: freebsd-arm@FreeBSD.org
          Reporter: prog@msobczak.com

A simple test with video framebuffer, composed of just:

1. open("/dev/fb0", ...)
2. mmap(...) on the file descriptor
3. memset(buf, ...) over any portion of the framebuffer area,

is very slow, compared to Linux Debian on the same board.

While the above test operates within a blink of an eye on Linux, its execution
on FreeBSD 13.x runs in apparently constant, but very low speed - taking about
2s to fill the whole framebuffer of reasonable size (whether 1280x1024 or
1024x768). Such timings make the whole concept of framebuffer somewhat useless.

While the test runs, the main console also displays a number of messages as
already reported in:

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=241428

It looks as if there is some checking/monitoring/etc. of every single write
while they traverse through the VM layers. Or, perhaps, a misconfigured
orchestration with the underlying hardware (framer DMA, etc.).

-- 
You are receiving this mail because:
You are the assignee for the bug.