Kiichi Kameda wrote: > I have been porting Xenomai-2.0.2 to SH(SuperH) architecture.
Cool! > Currently almost all functions work well. And, I am mesuring the performance > from user-space program using posix skin on a 240MHz SH7750R(SH4) machine, > mainly 1 ms periodic dispatch latency. The measured data shows small > latency(tens of micro seconds) when system has a light workload. > In case of heavy workload such as frequent linux command input, the latency > increases to some 200 micro seconds, though. If you are looking for real heavy load: cache benchmarks tend to stress your system most (e.g. http://www.cwi.nl/~manegold/Calibrator). Combine them with heavy i/o load (flood ping etc.). Anyway, 200 us for a 240 MHz system doesn't sound totally unrealistic. But I do not know the sh4 architecture to give a reliable estimation. What are your numbers when running latency in the other modes, i.e. without the need to switch to user space (mode 1, "-t1") or even without any context switch at all (mode 2, "-t2")? > > Following is the testsuit/latency/latency program(using native skin - > slightly modified) output with comment. > In case of posix skin, the data shows similar tendency. > > RTH|-----lat min|-----lat avg|-----lat max|-overrun|----lat best|---lat > worst > ...(no workload) > RTD| 333| 1400| 9733| 0| 333| > 27066 > RTD| 333| 1466| 34533| 0| 333| > 34533 > RTD| 266| 1400| 14533| 0| 266| > 34533 > RTD| 400| 1400| 14466| 0| 266| > 34533 > RTD| 333| 1333| 7533| 0| 266| > 34533 > RTD| 266| 1400| 14333| 0| 266| > 34533 > RTD| 333| 1400| 40866| 0| 266| > 40866 > RTD| 333| 1466| 25533| 0| 266| > 40866 > RTD| 266| 1400| 14400| 0| 266| > 40866 > RTD| 400| 1400| 13600| 0| 266| > 40866 > RTD| 266| 1400| 7466| 0| 266| > 40866 > RTD| 333| 1466| 40800| 0| 266| > 40866 > RTD| 333| 1400| 18466| 0| 266| > 40866 > RTD| 333| 1400| 13533| 0| 266| > 40866 > ... > RTD| 333| 1333| 7133| 0| 266| > 40866 > (telnet login) > RTD| 266| 4400| 111000| 0| 266| > 111000 > RTD| 333| 1400| 27266| 0| 266| > 111000 > RTD| 333| 1466| 28000| 0| 266| > 111000 > > RTD| 333| 1466| 33133| 0| 266| > 111000 > RTD| 333| 1466| 26800| 0| 266| > 111000 > (single ps aux command) > RTD| 333| 22800| 112533| 0| 266| > 112533 > RTD| 333| 1400| 19400| 0| 266| > 112533 > RTD| 266| 1466| 35000| 0| 266| > 112533 > RTD| 333| 1400| 7533| 0| 266| > 112533 > RTD| 333| 1400| 15733| 0| 266| > 112533 > RTD| 266| 1866| 71333| 0| 266| > 112533 > RTD| 333| 9866| 105866| 0| 266| > 112533 > RTD| 266| 1400| 14400| 0| 266| > 112533 > > RTD| 266| 1400| 11266| 0| 266| > 112533 > RTD| 400| 1466| 50133| 0| 266| > 112533 > RTD| 333| 3066| 116866| 0| 266| > 116866 > (successive ps aux command) > RTD| 1266| 15933| 218866| 0| 266| > 218866 > RTD| 1266| 2400| 76666| 0| 266| > 218866 > RTD| 333| 1400| 15000| 0| 266| > 218866 > RTD| 266| 1400| 27600| 0| 266| > 218866 > RTD| 400| 1400| 15333| 0| 266| > 218866 > RTD| 266| 1333| 6933| 0| 266| > 218866 > RTD| 333| 1400| 16533| 0| 266| > 218866 > RTD| 400| 1800| 75933| 0| 266| > 218866 > > > It is enough possible I have misported the Xenomai to SH, but I also think > Xenomai user-space program(primary mode) suffers such extra latency when > Linux kernel runs Linux programs. > > I will appreciate any suggestion for latency improvement. Very helpful for understanding what happens on your system is the ipipe latency tracer. We have support for x86 and ppc so far, and there are "templates" for porting it to other archs available from Ingo Molnar's original patch. Unfortunately, even the latter does not yet include sh4 support, so porting it would be a real pioneer work. :) But, basically, it can be as simple as writing an mcount stub in assembly to call the actual tracing function. See x86 on this. Jan
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