Re: PREEMPT_RT vs ADEOS: the numbers, part 1

[Ingo Molnar <mingo@elte.hu>]

a couple of other wrokloads that are easy to measure and are useful for 
triggering worst-case latencies:

hackbench:

  http://developer.osdl.org/craiger/hackbench/
  http://developer.osdl.org/craiger/hackbench/src/hackbench.c

it creates tons of threads and does message-passing between them. E.g.  
"hackbench 50" or "hackbench 100" is a pretty good test.

i use 40 copies of LTP running in parallel:

   while true; do ./runalltests.sh -x 40; done

this is good at triggering worst-case latencies too. Plus dbench is good 
too:

  http://samba.org/ftp/tridge/dbench/
  http://samba.org/ftp/tridge/dbench/dbench-3.03.tar.gz

  # dbench-3.03> ./dbench 50 -c ./client.txt

also, there's a very good on-host IRQ-latency measurement tool as well:

   http://www.affenbande.org/~tapas/wiki/index.php?rtc_wakeup

this uses TSC timestamping to detect wall-clock delays of the RTC 
interrupt. The tools jumps through lots of hoops to make sure the 
numbers are reliable. If you run it under the -RT kernel then run the 
RTC IRQ thread at a higher-than-all-other-threads priority:

  chrt -f 95 -p `pidof 'IRQ 8'`
  ./rtc_wakeup -f 1024 -t 100000

(when you run it, and if you also have RTC_HISTOGRAM enabled in your 
.config, then the kernel will print a histogram when you stop 
rtc_wakeup, so you've got two sources of information.)

	Ingo