I'm quite new to linux-rt. I'm trying to get a usable RT kernel on an Ubuntu 11.10 system. It has an nVidia Quadro NVS 285 video card and I'm trying to get the binary drivers working, too. I've built the 3.0.25 kernel with the rt44 patcheset applied. I've also modified it slightly so that migrate_enable, migrate_disable and __init_rt_mutex are exported using EXPORT_SYMBOL rather than EXPORT_SYMBOL_GPL (note I am aware of the legal issues surrounding this and won't be distributing the resulting kernel or source). I've then patched the nVidia driver source, replacing atomic_spinlock with raw_spinlock, down/up with mutex_lock/mutex_unlock and semaphores with mutexes. The resulting system runs and has quite good RT performance (max latency <20us reported by cyclictest, at least on short tests with full Ubuntu desktop running). However, the performance of X is dire - I get about two screen updates per second. The mouse still moves smoothly, but everything else only updates once or twice per second. It seems to be something quite far down the graphics processing chain that is slow, not individual operations - for instance, opening a page in Firefox doesn't take much longer than usual, it's just that I get no response at all for nearly a second and then the rendered page appears. It's like the screen is rendered into a buffer very fast but then flipping that buffer to the display is very slow. Does anyone have any suggestions for what might cause this or tools for tracking down where the problem comes from? I've spent a couple of days googling now with no success. Thanks for any help, Tom -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
