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This note includes:
Process Performance State Manager (PPSM) is a static library that implements the Enhanced Intel SpeedStep Technology (EIST), and System State S3 (Suspend to RAM) and S5 (Suspend to Disk) power management support.
PPSM supports the following power management modes:
By default, the system remains in the C0 state at the maximum clock rate. Whenever the CPU idle thread is running, the C1 state is entered.
You can:
For more information about the Enhanced Intel SpeedStep Technology, see http://www.intel.com/support/processors/sb/CS-028855.htm.
The PPSM library (libppsm.a) includes the following:
You normally call these functions in the following order:
void * ppsm_init( int verbose,
int prio,
int interval,
int scale_factor,
int lower,
int upper,
int policy);
This function creates the device structure and starts the CPU load-accounting threads for each CPU. The arguments are:
The ppsm_init() function returns a handle that you need to pass to the other PPSM functions, or NULL if the initialization failed (see the system log for details).
void ppsm_fini( void *handle);
This function stops the CPU accounting threads and releases the resources used by the PPSM library. The only argument is the handle returned by ppsm_init().
int ppsm_sys_mode( void *handle,
int mode );
This function sets the system-wide sleep mode. The arguments are:
The ppsm_sys_mode() function returns -1 if an error occurred; if the function succeeds, it doesn't return.
int ppsm_set_polling_interval( void *handle,
int interval,
int scale_factor );
This function sets the polling interval and the scaling factor. The arguments are:
The ppsm_set_polling_interval() function returns -1 on error (e.g. interval is less than 1).
int ppsm_set_threshold( void *handle,
int lower,
int upper );
This function sets the upper and lower threshold values for CPU loading. The arguments are:
The ppsm_set_threshold() function returns -1 on error (e.g. lower is less than 0, or lower is greater than upper).
int ppsm_get_cpuload( void *handle,
int cpu );
This function gets the current CPU load. The arguments are:
This function returns the per cent load for the specified CPU, or -1 if an error occurred (e.g. the CPU index is out of range).
int ppsm_get_cpufreq( void *handle,
int cpu );
This function gets the current CPU frequency. The arguments are:
The ppsm_get_cpufreq() function returns the current CPU frequency, in MHz, or -1 if an error occurred (e.g. the CPU index is out of range).
int ppsm_speedstep_enable( void *handle);
This function enables the SpeedStep functionality, which is disabled by default after you call ppsm_init(). This automatically sets the policy to PPSM_POLICY_ADAPTIVE. The only argument is the handle returned by ppsm_init().
The ppsm_speedstep_enable() function returns -1 on error.
int ppsm_speedstep_disable( void *handle);
This function disables the SpeedStep functionality (by default after you call ppsm_init(), the SpeedStep is disabled). This automatically sets the policy to PPSM_POLICY_NONE. The only argument is the handle returned by ppsm_init().
The ppsm_speedstep_disable() function returns -1 on error.
int ppsm_set_policy( void *handle,
int policy );
This function sets the power-management policy (by default after you call ppsm_init(), it's PPSM_POLICY_NONE). The arguments are:
The ppsm_set_policy() function returns -1 on error.
int ppsm_set_notify_handler( void *handle,
FnNotifyCbck cbx,
void *clientinfo );
This function registers a notification handler that you want to be called whenever there's a state change. The arguments are:
The ppsm_set_notify_handler() function returns -1 on error.
The prototype of the handler is as follows:
void my_handler ( void *handle,
int cpuid,
void *clientinfo );
Whenever the performance state changes, the library calls this function, passing the following:
The handler doesn't return anything.
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