i have released the -V0.7.47-29 Real-Time Preemption patch, which can be
downloaded from the usual place:
http://redhat.com/~mingo/realtime-preempt/
it's a fixes and speedups release. Changes since -47-20:
- x64 fixes (Michal Schmidt)
- cpufreq fix (Esben Nielsen)
- CONFIG_RT_DEADLOCK_DETECT build fix (Michal Schmidt)
- MAX_USER_RT_PRIO fix (Steven Rostedt)
there are more microoptimizations to the spin_lock/unlock hotpath:
- the caching of mutex_getprio() priority in p->normal_prio
- the mutex lock/unlock paths are now all fall-through. (Found a gcc
bug, it mishandles __builtin_expect() in certain cases and produces
correct but suboptimal code - we are working it around now.)
- reduced the amount of recursive preemption-counter bumps via the use
of raw spinlocks
- rely on the preemption-counter instead of IRQs-off sections
These changes brought the PREEMPT_RT overhead significantly down on
hackbench workloads (clearly a worst-case test for PREEMPT_RT overhead).
Would be interesting to see what kind of system time overhead PREEMPT_RT
now causes for e.g. jack_test workloads.
to build a -V0.7.47-29 tree, the following patches should to be applied:
http://kernel.org/pub/linux/kernel/v2.6/linux-2.6.11.tar.bz2
http://kernel.org/pub/linux/kernel/v2.6/testing/patch-2.6.12-rc6.bz2
http://redhat.com/~mingo/realtime-preempt/realtime-preempt-2.6.12-rc6-V0.7.47-29
Ingo
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