Messages in this thread | | | Date | Wed, 17 Nov 2004 00:11:45 +0100 | From | Ingo Molnar <> | Subject | Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm1-V0.7.27-3 |
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* Florian Schmidt <mista.tapas@gmx.net> wrote:
> hmm, the output doens't look so much different (or am i just blind?). > maybe i need to do make clean before building with this patch applied?
the trace is fine, note the extra 0x08000000:
> 5 88010003 0.000ms (+0.000ms): try_to_wake_up (wake_up_process) > 5 88010003 0.000ms (+0.000ms): (0) ((1)) > 5 88010002 0.000ms (+0.000ms): preempt_schedule (try_to_wake_up) > 5 88010002 0.000ms (+0.000ms): wake_up_process (redirect_hardirq) ^--- this one > 5 88010001 0.000ms (+0.000ms): preempt_schedule (__do_IRQ) > 5 88010001 0.000ms (+0.000ms): irq_exit (do_IRQ) > 5 88000002 0.000ms (+0.000ms): do_softirq (irq_exit) > 5 88000002 0.001ms (+0.990ms): __do_softirq (do_softirq) > 5 08000000 0.991ms (+0.000ms): preempt_schedule (_mmx_memcpy) > 5 98000000 0.991ms (+0.000ms): __schedule (preempt_schedule)
it was zero before - indeed hard to notice optically :-|
found the reason for this latency meanwhile: it's kernel_fpu_begin() and kernel_fpu_end() disabling/enabling preemption. (these are used by the mmx memcpy's)
i've uploaded the -11 patch with a preliminary fix:
http://redhat.com/~mingo/realtime-preempt/
which turns off the FPU-based ops if PREEMPT_RT is specified. The speed difference should be small but the latency difference is large ...
could you try -11, do you still see these large latencies?
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