Re: [PATCH] Preemptive Kernel for Ingo's O(1) scheduler

[george anzinger <george@mvista.com>]

Robert Love wrote:
> 
> A version of preempt-kernel is now available for Ingo's O(1) scheduler.

Great!  Well done.
> 
> For 2.5.2-pre11:
>         ftp://ftp.kernel.org/pub/linux/kernel/people/rml/preempt-kernel/v2.5/preempt-kernel-rml-2.5.2-pre11-1.patch
> For 2.4.18-pre3 + sched-O1-H6:
>         ftp://ftp.kernel.org/pub/linux/kernel/people/rml/preempt-kernel/v2.4/ingo-O1-sched/preempt-kernel-rml-2.4.18-pre3-ingo-1.patch
> 
> Because of changes in load_balance, I suggest not using preempt-kernel
> and an additional sched update on 2.5.  I'll update as the patches are
> merged into 2.5.
> 
> Making the kernel fully preemptible should be synergistic with Ingo's
> scheduler with its faster task dispatch time and better RT support.
> 
> Getting the two to play together was not hard, albeit a bit of a pain.
> The actually scheduling support is less, due to the simplified schedule
> and schedule_tail, although there is added code for making the per-CPU
> runqueues preempt-safe.
> 
> Benchmarks:
> 
> 2.5.2-pre11 dbench 16:          24.5364 MB/s
> 2.5.2-pre11-preempt dbench 16:  27.5192 MB/s
> 
> 2.5.2-pre11 latencytest:
> worst-case latency is 18.7ms with 96% scheduling latency on-time
> 2.5.2-pre11-preempt latencytest:
> 6ms (<1.5ms in all but disk write) with 99.9% scheduling latency on-time
> 
> 2.5.2-pre11-preempt avg latency is 1.1ms (for an arbitray work-load I
> tested with).  The obstacle for sub-ms average latency is still the
> long-held spinlocks that can be 100ms+.
> 
> Full ChangeLog:
> 
> - make preempt-kernel and Ingo's O(1) scheduler play nicely
> 
> - (2.5 only) more include additions
> 
> - various cleanups and such
> 
> Comments, patches, etc. are appreciated.  While it is running stable
> here in both SMP and UP on both 2.4 and 2.5, more testing could reveal
> problems.  Also, some optimization could be done at this point to
> hopefully reduce overhead.  Enjoy,
> 
>         Robert Love

-- 
George           george@mvista.com
High-res-timers: http://sourceforge.net/projects/high-res-timers/
Real time sched: http://sourceforge.net/projects/rtsched/