Messages in this thread | | | Date | Wed, 24 Mar 2004 14:57:20 +0100 | From | Takashi Iwai <> | Subject | Re: CONFIG_PREEMPT and server workloads |
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At Sat, 20 Mar 2004 16:03:11 +0100, Andrea Arcangeli wrote: > > On Sat, Mar 20, 2004 at 06:51:11AM -0800, William Lee Irwin III wrote: > > I may have missed one of his posts where he gave the results from the > > RT test suite. I found a list of functions with some kind of numbers, > > though I didn't see a description of what those numbers were and was > > looking for something more detailed (e.g. the output of the RT > > instrumentation things he had with and without preempt). This is all > > mostly curiosity and sort of hoping this gets carried out vaguely > > scientifically anyway, so I'm not really arguing one way or the other. > > agreed. what I've seen so far is a great number of graphs, they were > scientific enough for my needs and covering real life different > workloads, but I'm not sure what Takashi published exactly, you may want > to discuss it with him.
sorry, there is no exact descrption (yet) in public, except for the pdf of slides i presented ago:
http://www.alsa-project.org/~iwai/audio-latency.pdf
the data there are already old (based on 2.6.0-test9), and were measured by the old version of latency-test program (modifed version from Benno Senor's latencytest suite).
basically, the latency-test program measures the latency between the time of (periodical) irq and the time when user RT-thread is woken up under different workloads. the user thread can perform an artificial CPU load (busy loop) to simulate the situation that any RT process does a heavy job.
the resultant plot shows the critical deadline, the total latency and the CPU latency (busy loop) responses, as you can see in the above pdf.
the latest version of latency-test suite is found at
http://www.alsa-project.org/~iwai/latencytest-0.5.3.tar.gz
it uses its own kernel module to generate irqs from RTC and to trace stacks.
i'll show the results of the recent kernels tomorrow...
-- Takashi Iwai <tiwai@suse.de> ALSA Developer - www.alsa-project.org - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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