Creating a CPU Reserve

rk_reserve_t rk_cpu_reserve_create(rk_resource_set_t rs,cpu_reserve_attr_t attr)

Creates a CPU reservation and attaches it to resource set rs. The attributes of the CPU reservation are specified by the attr parameter, that is a pointer to a cpu_reserve_attr structure defined as follows:

struct cpu_reserve_attr {    


struct timespec compute_time;   


struct timespec period;    


struct timespec deadline;   


struct timespec blocking_time;   


struct timespec start_time;   


rk_reserve_param_data_t reserve_type; 


ticket_type_t           ticket_type;  


unsigned long           quota_tickets;  


cpu_tick_data_t         ticket_age;  

};

The amount of CPU reservation is specified by struct timespec computed_time and struct timespec period. The struct timespec deadline parameter is the relative deadline used by Deadline Monotonic or Earliest Deadline First, whereas struct timespec blocking_time and struct timespec start_time are the reserve blocking time (used for admission control) and start time respectively.

Parameters for CPU reservation are passed using the rk_reserve_param_t reserve_type field, that let you specify the enforcement and replenishment modes. Currently, LinuxRK supports the RSV_HARD, RSV_FIRM, and RSV_SOFT enforcement modes:

• RSV_HARD: guaranteed to receive the specified amount on success. After receiving the specified amount of time, the reserve is depleted.
• RSV_FIRM: guaranteed to receive the specified amount on success. If resource is still available after using up guaranteed amount, it will compete against non-reserved tasks for more.
• RSV_SOFT: guaranteed to receive the specified amount on success. If resource is still available after using up guaranteed amount, it will compete against all tasks for more.

Replenishment modes:

• RSV_HARD: If a reserve uses more than the reserved time in a period, the extra time will be subtracted from the available time in the following period.
• RSV_SOFT: The available time is always replenished to the reserved value.

Returns data structure rk_reserve_t on success and NULL_RESERVE on failure.