kwin XRENDER faster than OopenGL?

[Duncan]

Martin Bednár posted on Wed, 14 Sep 2011 14:08:25 +0200 as excerpted:

> Hi all,
> 
> Getting fed up with kwin's bad performance on several computers, I
> decided to play around with the settings, and ended up using XRender
> everywhere, because it is snappier.
> 
> Now I'm left wondering : is it kwin or crappy drivers? All the cards are
> entry-level integrated solutions (Everyone's represented : Intel, ATI,
> Nvidia), so no high performance is expected, but still, they should be
> enough for a window manager...
> 
> Any thoughts?

While the performance of individual hardware may vary, one point that's 
unarguable about xrender is that quite a number of effects simply won't 
work at all with xrender -- they require opengl.  Window translucency 
works with xrender, as does desktop-grid and present-windows, and that's 
enough for some and more-by-two than kde3, but they headline effects, 
cube, flip-switch, wobbly-windows, fall-apart/explode... require opengl, 
as do a couple of the arguably more useful effects, zoom in its various 
forms and track-mouse.

When I switched from kde3, I already needed window translucency as I had 
incorporated it into my workflow to the extent that it was quite 
difficult to do without. (With focus-follows-mouse but not auto-raise and 
the translucency levels set correctly, it can be quite useful to setup a 
couple partially overlapping windows, putting one on top then shifting 
the mouse so the other gets focus and can be typed into "through" the 
other one, while referencing the info in the top-but-inactive window.  
Given my activity on various lists, this was a very useful mode for me, 
answering questions about the one window while typing into the other one 
but being able to see them both, one thru the other.)

When I initially switched, I had a card (an old Radeon 92xx series card, 
r2xx chip) that was hardware limited to a 2048 px square for opengl, 
while I run dual monitors, stacked, for 1920x2160 (that's my current 
setup, dual 16:9 1920x1080, 1080p HDTV, at the time it was dual 4:3 
1600x1200 CRTs, for 1600x2400, but the problem was the same, one 
dimension > 2048).  Thus, I was limited to xrender -- no choice for 
OpenGL.

I upgraded to a Radeon hd4650 (rv730 chip) in part to get decent OpenGL 
and the other effects, and I've been quite happy with it indeed.  As it 
happened, that was actually quite a good choice in hardware (better than 
the in-theory better hd47xx and hd48xx series, apparently, at least on 
Linux, based on various complaints I've seen about the higher hd4xxx 
series), *AND* in practice, as I'm in my 40s and my near vision isn't 
what it used to be, and a properly working hardware-accelerated zoom is 
something I'd be loath to do without, now.  The mouse-tracker is also 
very handy, and I appreciate some of the eye-candy effects as well.  The 
acceleration is actually snappy enough that I set animation speed to slow 
(on the old 9200 by contrast, I had to set translucency fade effect speed 
manually, to single-digit ms, since instant gave me basically no fade, 
but the next notch, 100 ms, was molasses, something like 30 seconds total 
switch time if I switched focus just once, getting over a minute behind 
if I switched focus multiple times).

Meanwhile, try turning off the blur effect on the all effects tab.  That 
effect is much more computation intensive than many, and a number of 
drivers unfortunately try to emulate the hardware instructions in 
software for hardware that won't support it, instead of simply telling 
kwin that it's unsupported.  Obviously, that's *VERY* slow.

There's another hardware effect that is sometimes emulated in software, 
lanczos.  Unfortunately this one apparently isn't associated with a 
specific effect but is rather used for several if available, but there's 
a blacklist for it that you can edit.  Edit your kwinrc (normally ~/.kde/
share/config/kwinrc or you can put one at the system level, in /usr/share/
config/ on many distributions) and search for [Blacklist].  You'll find 
two blacklist sections, one for blur and one for lanczos.  You should be 
able to add your chip or card to the blacklist, using the general format 
of the existing entries, altho you may have to experiment a bit or google 
to get it just right as I'm not really sure on the format specifics.  
(7.8.2, etc, are mesa versions, I believe.  You can add yours, or 
experiment with leaving that out to see if it blacklists it globally, 
etc.)

Other than that, if simply adjusting the animation speed (to fast or very 
fast) on the general tab doesn't help sufficiently, try using the all 
effects tab and the various individual effect configs to toggle on only 
the effects you really want/need, paying special attention to the various 
animations (especially routine stuff like focus triggered translucency 
fades and window opens/closes) as they'll slow things down.  The general 
tab doesn't really provide fine enough control for people with slower 
graphics who none-the-less want some of the opengl effects, but can do 
without some of the fades, etc, that end up being so slow on their system.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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