os.hpp has a number of dead and effectively unused methods that could be removed, including but not limited to:

 os::distribute_processes
 os::enable_vtime
 os::vtime_enabled
 os::default_file_open_flags
 os::do_you_want_to_debug (!?)
 os::is_debugger_attached
 SuspendResume::is_suspend_request

There's also os::bind_to_processor which is only implemented on Solaris and only used by CMS if enabling a diagnostic flag (BindCMSThreadToCPU) which defaults to false, which seems like a reasonable candidate for deprecation and removal.