Re: [patch] Real-Time Preemption, -RT-2.6.13-rc4-V0.7.53-01, High Resolution Timers & RCU-tasklist features

[Ryan Brown <some.nzguy@gmail.com>]

is there a patch available for -rc6?

On 8/11/05, Ingo Molnar <mingo@elte.hu> wrote:
> 
> i have released the -53-01 Real-Time Preemption patch, which can be
> downloaded from:
> 
>   http://redhat.com/~mingo/realtime-preempt/
> 
> there are two new features in this release, which justified the jump
> from .52 to .53:
> 
>  - the inclusion of the High Resolution Timers patch, written by
>    George Anzinger, and ported/improved/cleaned-up by Thomas Gleixner.
> 
>  - the inclusion of the RCU tasklist_lock patch from Paul McKenney.
> 
> the HRT patch from George Anzinger is a crutial piece of real-time
> infrastructure. The version included in the -RT tree supports both PIT
> and local APIC timer driven variable-rate timer interrupts.
> 
> Thomas Glexiner, besides porting it to PREEMPT_RT, cleaning it up,
> adding the local APIC timer support has also added the
> CONFIG_HIGH_RES_TIMERS_DYN_PRIO feature, which pushes priority
> inheritance into the high-res timer space. Furthermore, Thomas has
> extended nanosleep to use HR timers, if the task is RT. This makes it
> easier to test HRT functionality.
> 
> NOTE: there's a new softirq, softirq-hrtimer (PID 8 on UP x86), which
> should be chrt-ed to higher than SCHED_FIFO-50 if HR timer interrupts
> are the most important latencies in the system. E.g.:
> 
>   chrt -f 90 -p 8
> 
> the RCU tasklist-lock patch is a small but important feature from Paul
> McKenney which enables good HRT latencies: the HRT patch, when using
> POSIX timers, would use a signal-sending codepath that depends on the
> tasklist_lock, and thus the (quite high) tasklist_lock latencies
> controlled the latency of HR timers - defeating much of the benefits of
> HR timers. With the RCU tasklist-lock the signal sending path is now
> RCU-read locked, with no locking dependency, and thus excellent
> worst-case latencies.
> 
> given these changes, some (mostly build-related) regressions are to be
> expected. Only the x86 architecture is expected to work for now.
> 
> to build a -V0.7.53-01 tree, the following patches should to be applied:
> 
>    http://kernel.org/pub/linux/kernel/v2.6/linux-2.6.12.tar.bz2
>    http://kernel.org/pub/linux/kernel/v2.6/testing/patch-2.6.13-rc4.bz2
>    http://redhat.com/~mingo/realtime-preempt/realtime-preempt-2.6.13-rc4-RT-V0.7.53-01
> 
> patches, bugreports and any other feedback welcome,
> 
>         Ingo
> -
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