the foreground and background colours. In bitblt_text functions, compare
values to this cache and don't re-draw the characters if they haven't changed.
When invalidating the display, clear this cache in order to force characters
to be redrawn; also force full redraws between suspend/resume pairs since odd
artifacts can otherwise result.
When scrolling the display (which is where most time is spent within the vt
driver) this yields a significant performance improvement if most lines are
less than the width of the terminal, since this avoids re-drawing blanks on
top of blanks.
(Note that "re-drawing" here includes writing to the VGA text mode buffer; on
virtualized systems this can be extremely slow since it triggers a glyph
being rendered onto a 640x480 screen).
On a c5.4xlarge EC2 instance (with emulated text mode VGA) this cuts the time
spent in vt(4) during the kernel boot from 1200 ms to 700ms; on my laptop
(with a 3200x1800 display) the corresponding time is reduced from 970 ms down
to 155 ms.
Reviewed by: imp, cem
Approved by: re (gjb)
Relnotes: Significant speedup in vt(4) and the system boot generally.
Differential Revision: https://reviews.freebsd.org/D16723
Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.
The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
The main purpose of this feature is to be able to unload a KMS driver.
When going back from the current vt(4) backend to the previous backend,
the previous backend is reinitialized with the special VDF_DOWNGRADE
flag set. Then the current driver is terminated with the new "vd_fini"
callback.
In the case of vt_fb and vt_vga, this allows the former to pass the
vgapci device vt_fb used to vt_vga so the device can be rePOSTed.
Differential Revision: https://reviews.freebsd.org/D687
suspend/resume
The goal is to avoid that the vt(4) resume happens before the video
display is resumed. The original patch was provided by Andriy Gapon.
This new patch registers the handlers in vt_upgrade(). This is done
once, thanks to the VDF_ASYNC flag. I abused this flag because it was
already abused by the keyboard allocation. The event handlers then call
the backend if it provides callbacks for suspend/resume.
Differential Revision: https://reviews.freebsd.org/D1004
On behalf of: dumbbell
MFC after: 2 weeks
rather than only drivers attached later on. This involves a small amount of
code duplication with dev/fb/fbd.c, which will fixed later on.
Also improve performance of vt_blank() by making it not read from the
framebuffer unnecessarily.
