Re: 3D OpenGL applications eat CPU ressources

["Émeric Maschino" <emeric.maschino@gmail.com>]

2010/2/3 Stephane Marchesin <stephane.marchesin@gmail.com>:
> No, you are right they don't trigger MCA. Hmm I didn't have any of
> those back then, my lockups came from the bus mostly...

Thank you for clarifying this point.

> Really if you have such lockups they may also happen on x86, did you
> try the card there?

Yes, I have no problem with this (AGP Pro 4x) graphics adapter (ATI
FireGL X1) in x86 hardware.

> At this point your best bet is probably replay the crashing sequence
> until you can reduce it to the offending couple of commands.

OK. Are the commands you're talking about the argument passed in the
various ioctl() calls logged when stracing the offending OpenGL
application? For example, strace glxgears gives lines like:
ioctl(4, 0xc0106451, 0x60000fffffd52d30) = 0
ioctl(4, 0xc0186419, 0x60000fffffd52d30) = 0
ioctl(4, 0x40106459, 0x60000fffffd52d58) = 0
where 4 is the file descriptor of /dev/dri/card0. Are 0xc0106451,
0xc0186419 or 0x40106459 the commands passed to the GPU?

I don't know if it's related to GPU lockup or not (I mean, being the
cause or a consequence), but I've also noticed in the strace glxgears
logs (or even simple application like glxinfo) that most of the read()
calls to /tmp/.X11-unix/X0 fail, whereas the writev() calls seem to
succeed:
poll([{fd=3, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=3, revents=POLLOUT}])
writev(3, [{"\222\0\3\0\4\0\0\0\0\0\0\0", 12}, {NULL, 0}, {"", 0}], 3) = 12
poll([{fd=3, events=POLLIN}], 1, -1)    = 1 ([{fd=3, revents=POLLIN}])
read(3, "\1\0*\0\0\0\0\0\4\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0",
4096) = 32
read(3, 0x60000000000093e4, 4096)       = -1 EAGAIN (Resource
temporarily unavailable)
where 3 is the file descriptor of /tmp/.X11-unix/X0

Émeric

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