linux/Documentation/trace/events-power.txt
<<
>>
Prefs
   1
   2                        Subsystem Trace Points: power
   3
   4The power tracing system captures events related to power transitions
   5within the kernel. Broadly speaking there are three major subheadings:
   6
   7  o Power state switch which reports events related to suspend (S-states),
   8     cpuidle (C-states) and cpufreq (P-states)
   9  o System clock related changes
  10  o Power domains related changes and transitions
  11
  12This document describes what each of the tracepoints is and why they
  13might be useful.
  14
  15Cf. include/trace/events/power.h for the events definitions.
  16
  171. Power state switch events
  18============================
  19
  201.1 New trace API
  21-----------------
  22
  23A 'cpu' event class gathers the CPU-related events: cpuidle and
  24cpufreq.
  25
  26cpu_idle                "state=%lu cpu_id=%lu"
  27cpu_frequency           "state=%lu cpu_id=%lu"
  28
  29A suspend event is used to indicate the system going in and out of the
  30suspend mode:
  31
  32machine_suspend         "state=%lu"
  33
  34
  35Note: the value of '-1' or '4294967295' for state means an exit from the current state,
  36i.e. trace_cpu_idle(4, smp_processor_id()) means that the system
  37enters the idle state 4, while trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id())
  38means that the system exits the previous idle state.
  39
  40The event which has 'state=4294967295' in the trace is very important to the user
  41space tools which are using it to detect the end of the current state, and so to
  42correctly draw the states diagrams and to calculate accurate statistics etc.
  43
  441.2 DEPRECATED trace API
  45------------------------
  46
  47A new Kconfig option CONFIG_EVENT_POWER_TRACING_DEPRECATED with the default value of
  48'y' has been created. This allows the legacy trace power API to be used conjointly
  49with the new trace API.
  50The Kconfig option, the old trace API (in include/trace/events/power.h) and the
  51old trace points will disappear in a future release (namely 2.6.41).
  52
  53power_start             "type=%lu state=%lu cpu_id=%lu"
  54power_frequency         "type=%lu state=%lu cpu_id=%lu"
  55power_end               "cpu_id=%lu"
  56
  57The 'type' parameter takes one of those macros:
  58 . POWER_NONE   = 0,
  59 . POWER_CSTATE = 1,    /* C-State */
  60 . POWER_PSTATE = 2,    /* Frequency change or DVFS */
  61
  62The 'state' parameter is set depending on the type:
  63 . Target C-state for type=POWER_CSTATE,
  64 . Target frequency for type=POWER_PSTATE,
  65
  66power_end is used to indicate the exit of a state, corresponding to the latest
  67power_start event.
  68
  692. Clocks events
  70================
  71The clock events are used for clock enable/disable and for
  72clock rate change.
  73
  74clock_enable            "%s state=%lu cpu_id=%lu"
  75clock_disable           "%s state=%lu cpu_id=%lu"
  76clock_set_rate          "%s state=%lu cpu_id=%lu"
  77
  78The first parameter gives the clock name (e.g. "gpio1_iclk").
  79The second parameter is '1' for enable, '0' for disable, the target
  80clock rate for set_rate.
  81
  823. Power domains events
  83=======================
  84The power domain events are used for power domains transitions
  85
  86power_domain_target     "%s state=%lu cpu_id=%lu"
  87
  88The first parameter gives the power domain name (e.g. "mpu_pwrdm").
  89The second parameter is the power domain target state.
  90
  91
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.