To Whom it May Concern: We have been experiencing large latencies under a CONFIG_PREEMPT_RT_FULL kernel for the past year. Recently, with the help of Carsten Emde at OSADL, we've identified that the latencies are associated with the nouveau driver. Under a 3.8.11-rt8 kernel (as well as a 3.8.4-rt2 kernel), we've consistently seen latencies over 2ms. These latencies are reproducible in an average of 10 seconds by scrolling in a web browser. They are only present if the nouveau driver is compiled into the kernel. We've demonstrated the issue on two computers: * Core 2 Duo with a Nvidia Quadro FX 580 * Intel Atom with Nvidia Ion GT218 Steps to reproduce the issue: 1) Install a kernel with the nouveau driver on a machine with an Nvidia graphics adapter 2) Run cyclictest -m -p99 -i100 3) Find any scrollable web page and scroll up and down in a web browser (I've reproduced it using Chromium and Firefox). Is anyone else able to reproduce this issue? Are any of you using the nouveau driver and not experiencing large latencies? I have attached the output of lspci, the kernel config, and a latency trace for the first system. Thank you for any help, Johnathan Van Why Dynamic Robotics Laboratory Oregon State University -- 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
