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[Bug 873453] Re: odd timing behaviour on panda

 

Hi DaveL,
  daveg@panda-01:~$ cd /sys/devices/system/clocksource/
daveg@panda-01:/sys/devices/system/clocksource$ ls
clocksource0
daveg@panda-01:/sys/devices/system/clocksource$ cat clocksource0/
cat: clocksource0/: Is a directory
daveg@panda-01:/sys/devices/system/clocksource$ cd clocksource0/
daveg@panda-01:/sys/devices/system/clocksource/clocksource0$ ls
available_clocksource  current_clocksource
daveg@panda-01:/sys/devices/system/clocksource/clocksource0$ cat available_clocksource 
32k_counter 
daveg@panda-01:/sys/devices/system/clocksource/clocksource0$ cat current_clocksource 
32k_counter

ps -eaf|grep ntp  shows nothing (the ntpdate package is installed,
initlist list | grep time or ntp shows nothing).

Dave

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https://bugs.launchpad.net/bugs/873453

Title:
  odd timing behaviour on panda

Status in Linaro Texas Instruments Landing Team:
  New
Status in Linaro Ubuntu Evaluation Builds:
  New

Bug description:
  I've got a set of benchmarks that use clock_gettime like:

      clock_gettime(CLOCK_REALTIME, &tbefore);

      for(l=0;l<numloops;l++) {
         dostuff
      }

      clock_gettime(CLOCK_REALTIME, &tafter);

      nsdiff=(double)(tafter.tv_nsec - tbefore.tv_nsec);
      nsdiff+=1000000000.0 *(tafter.tv_sec - tbefore.tv_sec);

  
  and I've just reinstalled our local panda to using Linaro 11.09 (kernel 3.0.0-1404-linaro-lt-omap)
  and it's starting to get weird timing artifacts.

  For example:

  smarter_strlen_ldrd: ,102400, loops of ,62, bytes=6.054688 MB, transferred in ,3936768.000000 ns, giving, 1537.984331 MB/s
  smarter_strlen_ldrd: ,102400, loops of ,32, bytes=3.125000 MB, transferred in ,0.000000 ns, giving, inf MB/s
  smarter_strlen_ldrd: ,102400, loops of ,16, bytes=1.562500 MB, transferred in ,4180909.000000 ns, giving, 373.722557 MB/s

  Now there is no way that loop took 0.000000 ns!  Running the same
  binary on an older installation runs fine.

  Dave

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