Performance of X (x11perf vs framebuffer vs test program)

[Bilderbeek, Manuel]

Hello,

I did some performance measurements again and I'd like to hear your
comment.

I did the following tests, all on an 800x600x16bpp configuration, on a
Via Epia ML, 800MHz on CLE266
1) fill 500x500 rectangles in the Linux framebuffer device, using a
memset for each line (see a previous mail on xorg mailinglist),
compilation with -O1
2) fill 500x500 rectangles with Java and Qt (didn't make a difference)
on X  (see a previous mail on xorg mailinglist)
3) use x11perf -rect500

I did these experiments both an a Debian testing system with Xorg 6.9
and a 2.6.15 kernel for 486, using fbdev and via drivers, and on a
MontaVista Linux (MVL) 4.0.1, with an Xorg 6.8.2 installation
(configured as 'tinyX', with only the fbdev driver) and a 2.6.10 kernel
tailored for Via C3.

The results are the number of 500x500 rectangle fills per second.


On Debian
1) 172
2) fbdev driver: 50, via driver (with hardware acceleration): more than
about 2000
3) fbdev driver: 169, via driver (with hardware acceleration): 3550
4) as 2), but with the Rotate "CW" option: fbdev (driver says: using
shadowfb): 23, via (driver says: hardware acceleration disabled, using
shadowfb): 40
5) as 3), but with the Rotate "CW" option: fbdev (as above): 124, via
(as above): 79

On MVL:
1) 190
2) fbdev driver: 59
3) fbdev driver: 230
4) as 2), but with the Rotate "CW" option (as above): fbdev: 20
5) as 3), but with the Rotate "CW" option (as above): fbdev: 193


Some things about this are quite weird in my eyes:
1) how can the x11perf program be faster than the C program with memset?
2) why is (on fbdev driver), the Qt/Java program more than a factor 3
slower (see previous mails about this, "Overhead of X11"), while all CPU
load is in X, according to atop?
3) in connection with 2): why is x11perf performing so much better than
the Qt/Java prog? Is this test comparable?
4) (most interesting for the OpenChrome folks) how on earth can the via
driver be 50% slower than the fbdev driver, when the Rotate option is
set?


I'm not an in-depth X expert at all, that's why I'd like to ask for your
opinion once again... 

--
Kind regards,

Manuel Bilderbeek

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