How fast is the build-in function SHGetValueA function (shlwapi.h) in C++?

I have been in doubt about what should be a better approach:

1. To cache the registry and use it later (I won't be doing it multiple times).
2. To run this function when needed (if it is fast)

How can I measure the speed of this function?

int ReadUACRegistryKey(LPCWSTR key)
{
    LPCWSTR pszSubKey, pszValue = key;
    const std::wstring sPath = L"XXXXXXXXXXX";

    pszSubKey = sSearchPattern.c_str();
    DWORD dwType = 0;
    DWORD dwValue = 0;
    DWORD dwValueSize = sizeof(dwValue);

    int retval = SHGetValue(HKEY_LOCAL_MACHINE, pszSubKey, key, &dwType, &dwValue, &dwValueSize);
    if (retval != ERROR_SUCCESS)
    {
        Trace(TRACE_ERROR, _T("ERROR: Failed to retrieve Registry setting and check Input_Image format."));
    }

    return dwValue;
}```