Performance-Monitoring Counters Library, for Intel/AMD Processors and Linux

This example introduces
   rabbit command-line options --duration m,n --user m,n --os m,n
   an experiment to measure operating system activity

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Command-Line Options

--duration m,n

  m, n = 1-bit flag, default 0

  Some events may extend over several cycles.  Count occurrences (0)
  or cycles (1) associated with the event.

  Most events count occurences or cycles independent of this option.
  Use 'rabbit -d' for more information.

--user m,n
--os m,n

  m, n = 1-bit flag, default 1

  When enabled (1), events are counted if the Current Privilege Level
  is in user-mode or system-mode.  For the Pentium, user-mode is CPL
  3; for the Pentium Pro/II/III and Athlon it is 1, 2 or 3.  For the
  Pentium, system-mode is CPL 0, 1 or 2; for the Pentium Pro/II/III and
  Athlon it is 0.  When disabled (0), events are not counted.

  Formally, CPL 0 = OS kernel; 1, 2 = OS services; 3 = applications.
  Linux typically uses only CPL 0 and 3.

  On the Athlon, four counters are available.

  Be careful not to use '-o' when you mean '--o'.  '-o 0' will create
  and write to the directory '0' (-output).


Example

  To see what fraction of system activity is taken by the operating
  system and daemons, select the events simply to count cycles.  We
  use the same event in both counters, separating the user and system
  modes on a 200 MHz Pentium Pro running Linux 2.0.28 (h% is the prompt).

    h% rabbit --e 121 -d
    0x79 121  cycles processor is not halted
    0x79 121  cycles processor is not halted

  Since only two events are used, and we are only looking for an average, we
  do not need to sample frequently.  The first case is an idle system:

    h% rabbit -s 1 --e 121 --user 1,0 --os 0,1 sleep 150

    ------------------------   performance counters   ------------------------

    Host processor: h
    Command executed: sleep 150
    Options: --duration 0,0 --user 1,0 --os 0,1
    Options: --mesi 0xf,0xf --bus_agent 1,1 --compare 0,0 --invert 0,0
    Options: --Enable 1,1 --PC 1,1 --APIC 0,0
    Sampling: rate = 1 sample per second, 151 taken

    Event                                           Events          Events/sec
    ----------------------------------    ----------------    ----------------
    0x79 121  cpu_clk_unhalted                     1168492             7815.64
    0x79 121  cpu_clk_unhalted                 29900221370        199992202.93

    resource usage:
      time = 0.00 sec user, 0.00 sec sys, 149.51 sec real, 0.00% of cpu
      page reclaims, faults = 7, 59

  Almost all the system activity on an idle system occurs in a timed delay
  loop inside the scheduler, ultimately waiting for an interrupt.  Note that
  the Pentium II (450 MHz, Linux 2.0.36) will show different results, and you
  might have some fun trying to explain why:

    holmes% rabbit -s 1 --e 121 --user 1,0 --os 0,1 sleep 150

    ------------------------   performance counters   ------------------------

    Host processor: holmes
    Command executed: sleep 150
    Options: --duration 0,0 --user 1,0 --os 0,1
    Options: --mesi 0xf,0xf --bus_agent 1,1 --compare 0,0 --invert 0,0
    Options: --MMX 0x3f,0x3f
    Options: --Enable 1,1 --PC 1,1 --APIC 0,0
    Sampling: rate = 1 sample per second, 151 taken

    Event                                           Events          Events/sec
    ----------------------------------    ----------------    ----------------
    0x79 121  cpu_clk_unhalted                     1095160             7282.76
    0x79 121  cpu_clk_unhalted                    88178872           586384.85
    
    resource usage:
      time = 0.00 sec user, 0.01 sec sys, 150.38 sec real, 0.01% of cpu
      page reclaims, faults = 10, 73

  The second case is a user program with no system calls:

    h% rabbit -s 1 --e 121 --user 1,0 --os 0,1 foo
    < output from foo omitted >

    ------------------------   performance counters   ------------------------

    Host processor: h
    Command executed: foo
      command exited with non-zero status 33
    Options: --duration 0,0 --user 1,0 --os 0,1
    Options: --mesi 0xf,0xf --bus_agent 1,1 --compare 0,0 --invert 0,0
    Options: --Enable 1,1 --PC 1,1 --APIC 0,0
    Sampling: rate = 1 sample per second, 151 taken

    Event                                           Events          Events/sec
    ----------------------------------    ----------------    ----------------
    0x79 121  cpu_clk_unhalted                 30006478362        199621756.24
    0x79 121  cpu_clk_unhalted                    56859145           378262.40

    resource usage:
      time = 150.76 sec user, 0.05 sec sys, 150.32 sec real, 100.33% of cpu
      page reclaims, faults = 7, 50

  A simple check of the data,
         7815.64 + 199992202.93 = 200000018.57, and
    199621756.24 +    378262.40 = 200000018.64,
  shows that the operating system took about 378262.40 / 200000018.64 = 0.19%
  of the cycles otherwise available to the user program.  You can expect these
  numbers to vary somewhat, depending on system configuration and transitory
  conditions.