SDL_mixer & dual CPU starvation problem

SDL Development
1

Hi Guys,

Just noticed an odd problem with the following combination:
DUAL PentiumII 300 box
SDL-1.1.4
SDL_mixer-1.0.6
smpeg-0.4.0
linux 2.2.15 and linux 2.2.17

AlteredSaver on Linux uses the above libraries to play sounds.
Everything works well enough on a single CPU box, but when I try running
on a dual CPU machine, the application startup process is rather messed
up.

NORMAL CASE:============
W/o sound enabled, or on a single CPU box with sound, the app starts in
around 3 seconds.

PROBLEM CASE:

On a dual CPU box with sound enabled in saver settings, app. takes more
than 10 seconds, and you sometimes hear a couple of sections of the
music track as follows: after some time, a second long burst of sound,
then a gap, then another second of sound, then finally the whole thing
starts playing correctly.

If I use the AlteredSaver settings to launch plaympeg on the music track
as an ‘external helper’ (commercial version only) , everything works
fine - in this case, I am 'execvp’ing plaympeg myself rather than
letting SDL_mixer do it.

SO - looks like there might be some problem with the locking code in
SDL_mixer? If I boot the dual machine using a single CPU kernel, it
works fine.

QUESTION:

Is this a known issue? If not, what can I do to help?

Problem can be seen with free version of AlteredSaver at:
http://www.AlteredWorlds.com/linux/altered-2.3-full.tgz [15MB]

thanks,

Tom Gilbert
http://www.AlteredWorlds.com

2

Hi there,

I’m happy to report that this was not a problem with SDL.

Having upgraded the system to a new kernel [2.4.0-test9],
DRI CVS XFree86 4 and an AGP G400 the problem has gone away.

NVIDIAs driver FAQ contains a note to SMP users - must use
binutils >= 2.9.5 otherwise kernel spinlocks don’t work right.
Perhaps that’s what was going on - at any rate, nothing to do
with SDL.

thanks,

Tom Gilbert
http://www.AlteredWorlds.com

Tom Gilbert wrote:>

Hi Guys,

Just noticed an odd problem with the following combination:
DUAL PentiumII 300 box
SDL-1.1.4
SDL_mixer-1.0.6
smpeg-0.4.0
linux 2.2.15 and linux 2.2.17

AlteredSaver on Linux uses the above libraries to play sounds.
Everything works well enough on a single CPU box, but when I try running
on a dual CPU machine, the application startup process is rather messed
up.

NORMAL CASE:

W/o sound enabled, or on a single CPU box with sound, the app starts in
around 3 seconds.

PROBLEM CASE:

On a dual CPU box with sound enabled in saver settings, app. takes more
than 10 seconds, and you sometimes hear a couple of sections of the
music track as follows: after some time, a second long burst of sound,
then a gap, then another second of sound, then finally the whole thing
starts playing correctly.

If I use the AlteredSaver settings to launch plaympeg on the music track
as an ‘external helper’ (commercial version only) , everything works
fine - in this case, I am 'execvp’ing plaympeg myself rather than
letting SDL_mixer do it.

SO - looks like there might be some problem with the locking code in
SDL_mixer? If I boot the dual machine using a single CPU kernel, it
works fine.

QUESTION:

Is this a known issue? If not, what can I do to help?

Problem can be seen with free version of AlteredSaver at:
http://www.AlteredWorlds.com/linux/altered-2.3-full.tgz [15MB]

thanks,

Tom Gilbert
http://www.AlteredWorlds.com

3

Hi there,

I’m happy to report that this was not a problem with SDL.

Yay, it looked hairy. :slight_smile:

See ya,
-Sam Lantinga, Lead Programmer, Loki Entertainment Software