prthreadscope.rst (1657B)
1 PRThreadScope 2 ============= 3 4 The scope of an NSPR thread, specified as a parameter to 5 :ref:`PR_CreateThread` or returned by :ref:`PR_GetThreadScope`. 6 7 8 Syntax 9 ------ 10 11 .. code:: 12 13 #include <prthread.h> 14 15 typedef enum PRThreadScope { 16 PR_LOCAL_THREAD, 17 PR_GLOBAL_THREAD 18 PR_GLOBAL_BOUND_THREAD 19 } PRThreadScope; 20 21 22 Enumerators 23 ~~~~~~~~~~~ 24 25 ``PR_LOCAL_THREAD`` 26 A local thread, scheduled locally by NSPR within the process. 27 ``PR_GLOBAL_THREAD`` 28 A global thread, scheduled by the host OS. 29 ``PR_GLOBAL_BOUND_THREAD`` 30 A global bound (kernel) thread, scheduled by the host OS 31 32 33 Description 34 ----------- 35 36 An enumerator of type :ref:`PRThreadScope` specifies how a thread is 37 scheduled: either locally by NSPR within the process (a local thread) or 38 globally by the host (a global thread). 39 40 Global threads are scheduled by the host OS and compete with all other 41 threads on the host OS for resources. They are subject to fairly 42 sophisticated scheduling techniques. 43 44 Local threads are scheduled by NSPR within the process. The process is 45 assumed to be globally scheduled, but NSPR can manipulate local threads 46 without system intervention. In most cases, this leads to a significant 47 performance benefit. 48 49 However, on systems that require NSPR to make a distinction between 50 global and local threads, global threads are invariably required to do 51 any form of I/O. If a thread is likely to do a lot of I/O, making it a 52 global thread early is probably warranted. 53 54 On systems that don't make a distinction between local and global 55 threads, NSPR silently ignores the scheduling request. To find the scope 56 of the thread, call :ref:`PR_GetThreadScope`.