Summary
Get CPU performance parameters.
Declaration
#include <zircon/syscalls.h>
zx_status_t zx_system_get_performance_info(zx_handle_t resource,
uint32_t topic,
size_t count,
void* info,
size_t* output_count);
Description
zx_system_get_performance_info() requests CPU performance parameters maintained by the kernel. The
topic parameter indicates what specific information is desired.
count indicates the number of items to query. 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. The values stored in this array are undefined if the syscall returns an error.
output_count is updated with the number of info entries populated by the kernel on success. The value stored in this memory location is undefined if the syscall returns an error.
TOPICS
ZX_CPU_PERF_SCALE
count: Must be equal to the number of logical CPUs in the system.
info type: zx_cpu_performance_scale_t[count]
Returns an array of zx_cpu_performance_scale_t with entries indicating the current performance
scales (scalar values representing relative operating points) of each logical CPU in the system. The
values reflect the most recent call to zx_system_set_performance_info, even if the values have not
yet taken effect.
See RFC 0123 for further details on values and update protocols.
ZX_CPU_DEFAULT_PERF_SCALE
count: Must be equal to the number of logical CPUs in the system.
info type: zx_cpu_performance_scale_t[count]
Returns an array of zx_cpu_performance_scale_t with entries indicating the default performance
scales used during boot of each logical CPU in the system.
See RFC 0123 for further details.
Rights
resource must have resource kind ZX_RSRC_KIND_SYSTEM.
Return value
zx_system_get_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_ACCESS_DENIED resource is not in the range [ZX_RSRC_SYSTEM_CPU_BASE, ZX_RSRC_SYSTEM_CPU_BASE+1).
ZX_ERR_INVALID_ARGS topic, info, or output_count have invalid values.
ZX_ERR_OUT_OF_RANGE count does 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.