Summary
Set CPU performance parameters.
Declaration
#include <zircon/syscalls.h>
zx_status_t zx_system_set_performance_info(zx_handle_t resource,
uint32_t topic,
const void* info,
size_t count);
Description
zx_system_set_performance_info() sets CPU performance parameters maintained by the kernel. The
topic parameter indicates what specific parameters are affected.
count indicates the number of items to set. Topics may impose requirements on this value.
info is a pointer to a buffer of sufficient size to accommodate count entries of the type specified by topic.
TOPICS
ZX_CPU_PERF_SCALE
count: Must be non-zero and less than or equal to the number of logical CPUs in the system.
info type: zx_cpu_performance_scale_t[count]
An array of zx_cpu_performance_scale_t with entries specifying the performance scales (scalar
values representing relative operating points) of the respective logical CPUs in the system. Only
the CPUs specified in the array are updated, other CPUs are not affected.
Logical CPU numbers must be stored in increasing order in the array. The scale values are unsigned fixed point Q32.32 format. The scale values should indicate the relative performance of the CPUs, with 1.0 corresponding to the highest operating point of the fastest CPU in the system.
See RFC 0123 for further details on values and update protocols.
ZX_CPU_POWER_LIMIT
count: Must be non-zero and less than or equal to the number of logical CPUs in the system.
info type: zx_cpu_power_limit_t[count]
An array of zx_cpu_power_limit_t with entries specifying the energy limits (in nano-watts).
These values will then be used by the scheduler to constrain the power consumption of each
affected processor.
Rights
resource must have resource kind ZX_RSRC_KIND_SYSTEM.
Return value
zx_system_set_performance_info() returns ZX_OK on success. In the event of a failure, a
negative error value is returned.
Errors
ZX_ERR_BAD_HANDLE resource is not a valid handle.
ZX_ERR_WRONG_TYPE resource is not resource kind ZX_RSRC_KIND_SYSTEM.
ZX_ERR_OUT_OF_RANGE resource is not in the range [ZX_RSRC_SYSTEM_CPU_BASE, ZX_RSRC_SYSTEM_CPU_BASE+1).
ZX_ERR_INVALID_ARGS topic or info have invalid values or info has out-of-order entries.
ZX_ERR_OUT_OF_RANGE count or info entry values do not meet the requirements of the topic.
ZX_ERR_NO_MEMORY Failure due to lack of memory. There is no good way for userspace to handle this (unlikely) error. In a future build this error will no longer occur.