I am using Debian Lenny with 2.6.30 kernel on my Intel Atom Poulsbo chipset computer and I get the following messages in my dmesg when I start the X server:
[ 22.760737] mtrr: type mismatch for 3ffc0000,10000 old: write-back new: write-combining
[ 22.760805] mtrr: type mismatch for 3ff80000,40000 old: write-back new: write-combining
Jesse Barnes posted a summary of recent efforts to improve the Linux kernel's support for graphics, "in collaboration with the [framebuffer] guys, we've been working on enhancing the kernel's graphics subsystem in an attempt to bring some sanity to the Linux graphics world and avoid the situation we have now where several kernel and userspace drivers compete for control of graphics devices." He then explained, "there are several reasons to pull modesetting and proper multihead support into the kernel: suspend/resume, debugging (e.g. panic), non-X uses, and more reliable VT switch," going on to offer detail on each of these listed reasons. Jesse followed these explanations with an overview of the current status of the code:
"The current codebase is still incomplete in many ways: locking needs to be (re-)added around our various list manipulation paths, we need better initial configuration logic, only the Intel driver has any support (and it's still missing suspend/resume and accelerated FB functions), we need to check modes against monitor limitations (which come from EDID or the user), CVT and GTF based mode generation still isn't used by the DRM modesetting code, and much more. I'm hoping that by posting this now, we can get some ideas about what requirements other people have for graphics on Linux so we can prioritize our work."
2.4 kernel maintainer [story] Willy Tarreau ran some tests to compare Con Kolivas [interview]'s Staircase Deadline CPU scheduler [story] with Ingo Molnar [interview]'s new Completely Fair Scheduler [story]. He summarized his experiences:
"I think that CFS is based on a more promising concept but is less mature and is dangerous right now with certain workloads. SD shows some strange behaviours like not using all CPU available and a little jerkyness, but is more robust and may be the less risky solution for a first step towards a better scheduler in mainline, but it may also probably be the last O(1) scheduler, which may be replaced sometime later when CFS (or any other one) shows at the same time the smoothness of CFS and the robustness of SD."
Some debate was raised by logic added since CFS version 3 to automatically nice the X process for better GUI responsiveness. The CFS changelog comment labels the change as a usibility fix explaining, "automatic renicing of kernel threads such as keventd, OOM tasks and tasks doing privileged hardware access (such as Xorg)." Ingo posted a standalone patch demonstrating how these processes are detected and automatically niced, offering it for inclusion into Con's Staircase scheduler. Willy concurred that it was a good idea, "I think it could be a good idea since you recommend to renice X with SD. Most of the problem users are facing with renicing X is that they need to change their configs or scripts. If the kernel can reliably detect X and handle it differently, why not do it ?" Con was less convinced, "hmm well I have tried my very best to do all the changes without changing 'policy' as much as possible since that trips over so many emotive issues that noone can agree on, and I don't have a strong opinion on this as I thought it would be better for it to be a config option for X in userspace instead. Either way it needs to be turned on/off by admin and doing it by default in the kernel is... not universally accepted as good."