Geoff Chappell, Software Analyst
The SYSTEM_PROCESSOR_IDLE_INFORMATION structure is produced in the output buffer by a successful call to the following functions:
when given the information class SystemProcessorIdleInformation (0x2A).
The SYSTEM_PROCESSOR_IDLE_INFORMATION structure is not documented.
Microsoft does publish the practical equivalent of a C-language definition as type information in public symbol files, though not for the kernel, where the structure is prepared, nor even for low-level user-mode DLLs that interpret the structure, but for various higher-level user-mode DLLs such as URLMON.DLL and only then starting with version 6.2.
The SYSTEM_PROCESSOR_IDLE_INFORMATION is 0x30 bytes in both 32-bit and 64-bit Windows.