* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Threads
Survey
Document related concepts
Plan 9 from Bell Labs wikipedia , lookup
Library (computing) wikipedia , lookup
Berkeley Software Distribution wikipedia , lookup
Unix security wikipedia , lookup
Copland (operating system) wikipedia , lookup
Mobile operating system wikipedia , lookup
Spring (operating system) wikipedia , lookup
Distributed operating system wikipedia , lookup
Process management (computing) wikipedia , lookup
Transcript
Chapter 4: Threads Outline Overview Multithreading Models Thread Libraries Threading Issues Operating System Examples Windows XP Threads Linux Threads Operating System Concepts – 7th edition, Jan 23, 2005 4.2 Silberschatz, Galvin and Gagne ©2005 Objectives To introduce the notion of a thread — a fundamental unit of CPU utilization that forms the basis of multithreaded computer systems To discuss the APIs for the Pthreads, Win32, and Java thread libraries To examine issues related to multithreaded programming Operating System Concepts – 7th edition, Jan 23, 2005 4.3 Silberschatz, Galvin and Gagne ©2005 Single and Multithreaded Processes Operating System Concepts – 7th edition, Jan 23, 2005 4.4 Silberschatz, Galvin and Gagne ©2005 Benefits Responsiveness Resource Sharing Economy Utilization of MP Architectures Operating System Concepts – 7th edition, Jan 23, 2005 4.5 Silberschatz, Galvin and Gagne ©2005 Multicore Programming Multicore systems putting pressure on programmers, challenges include Dividing activities Balance Data splitting Data dependency Testing and debugging Operating System Concepts – 7th edition, Jan 23, 2005 4.6 Silberschatz, Galvin and Gagne ©2005 Multithreaded Server Architecture Operating System Concepts – 7th edition, Jan 23, 2005 4.7 Silberschatz, Galvin and Gagne ©2005 Concurrent Execution on a Single-core System Operating System Concepts – 7th edition, Jan 23, 2005 4.8 Silberschatz, Galvin and Gagne ©2005 Parallel Execution on a Multicore System Operating System Concepts – 7th edition, Jan 23, 2005 4.9 Silberschatz, Galvin and Gagne ©2005 User Threads Thread management done by user-level threads library Three primary thread libraries: POSIX Pthreads Win32 threads Java threads Operating System Concepts – 7th edition, Jan 23, 2005 4.10 Silberschatz, Galvin and Gagne ©2005 Kernel Threads Supported by the Kernel Examples Windows XP/2000 Solaris Linux Tru64 UNIX Mac OS X Operating System Concepts – 7th edition, Jan 23, 2005 4.11 Silberschatz, Galvin and Gagne ©2005 Multithreading Models Relationships between user threads and kernel threads Many-to-One One-to-One Many-to-Many Operating System Concepts – 7th edition, Jan 23, 2005 4.12 Silberschatz, Galvin and Gagne ©2005 Many-to-One Many user-level threads mapped to single kernel thread Thread management by thread library in user space efficient No concurrency Unable to run in MP Examples: Solaris Green Threads GNU Portable Threads Operating System Concepts – 7th edition, Jan 23, 2005 4.13 Silberschatz, Galvin and Gagne ©2005 Many-to-One Model Operating System Concepts – 7th edition, Jan 23, 2005 4.14 Silberschatz, Galvin and Gagne ©2005 One-to-One Each user-level thread maps to kernel thread More concurrency Able to run in MP Overhead of creating kernel threads Examples Windows NT/XP/2000 Linux Solaris 9 and later Operating System Concepts – 7th edition, Jan 23, 2005 4.15 Silberschatz, Galvin and Gagne ©2005 One-to-one Model Operating System Concepts – 7th edition, Jan 23, 2005 4.16 Silberschatz, Galvin and Gagne ©2005 Many-to-Many Model Allows many user level threads to be mapped to many kernel threads Concurrency Can run in MP Developers can create as many user threads as necessary Examples Solaris prior to version 9 Windows NT/2000 with the ThreadFiber package Operating System Concepts – 7th edition, Jan 23, 2005 4.17 Silberschatz, Galvin and Gagne ©2005 Many-to-Many Model Operating System Concepts – 7th edition, Jan 23, 2005 4.18 Silberschatz, Galvin and Gagne ©2005 Two-level Model Similar to M:M, except that it allows a user thread to be bound to kernel thread Examples IRIX HP-UX Tru64 UNIX Solaris 8 and earlier Operating System Concepts – 7th edition, Jan 23, 2005 4.19 Silberschatz, Galvin and Gagne ©2005 Two-level Model Operating System Concepts – 7th edition, Jan 23, 2005 4.20 Silberschatz, Galvin and Gagne ©2005 Thread Libraries Thread library provides programmer with API for creating and managing threads Two primary ways of implementing Library entirely in user space Kernel-level library supported by the OS Operating System Concepts – 7th edition, Jan 23, 2005 4.21 Silberschatz, Galvin and Gagne ©2005 Pthreads May be provided either as user-level or kernel-level A POSIX standard (IEEE 1003.1c) API for thread creation and synchronization API specifies behavior of the thread library, implementation is up to development of the library Common in UNIX operating systems (Solaris, Linux, Mac OS X) Operating System Concepts – 7th edition, Jan 23, 2005 4.22 Silberschatz, Galvin and Gagne ©2005 Java Threads Java threads are managed by the JVM Typically implemented using the threads model provided by underlying OS Java threads may be created by: Extending Thread class Implementing the Runnable interface Operating System Concepts – 7th edition, Jan 23, 2005 4.23 Silberschatz, Galvin and Gagne ©2005 Threading Issues Semantics of fork() and exec() system calls Thread cancellation Signal handling Thread pools Thread specific data Scheduler activations Operating System Concepts – 7th edition, Jan 23, 2005 4.24 Silberschatz, Galvin and Gagne ©2005 Semantics of fork() and exec() Does fork() duplicate only the calling thread or all threads? Which of the two versions of fork() to use depends on the application Exec() No immediately after fork() exec() after fork() Operating System Concepts – 7th edition, Jan 23, 2005 4.25 Silberschatz, Galvin and Gagne ©2005 Thread Cancellation Terminating a thread before it has finished Two general approaches: Asynchronous cancellation terminates the target thread immediately Deferred cancellation allows the target thread to periodically check if it should be cancelled Problems when resources have been allocated to a canceled thread or while in the midst of updating data sharing with other threads Operating System Concepts – 7th edition, Jan 23, 2005 4.26 Silberschatz, Galvin and Gagne ©2005 Signal Handling Signals are used in UNIX systems to notify a process that a particular event has occurred A signal handler is used to process signals 1. Signal is generated by particular event 2. Signal is delivered to a process 3. Signal is handled Synchronous vs. asynchronous signals Default vs. user-defined handlers Operating System Concepts – 7th edition, Jan 23, 2005 4.27 Silberschatz, Galvin and Gagne ©2005 Options to deliver signals in multithreaded programs: Deliver the signal to the thread to which the signal applies Deliver the signal to every thread in the process Deliver the signal to certain threads in the process Assign a specific thread to receive all signals for the process ex: kill(aid_t aid, int signal) pthread_kill(pthread_t tid, int signal) Operating System Concepts – 7th edition, Jan 23, 2005 4.28 Silberschatz, Galvin and Gagne ©2005 Thread Pools Create a number of threads in a pool where they await work Advantages: Usually slightly faster to service a request with an existing thread than create a new thread Allows the number of threads in the application(s) to be bound to the size of the pool Ex: QueueUserWorkItem(LPTHREAD_START_ROUTI NE Function, PVOID Param, ULONG Flags) in Win32 API java.util.concurrent package in Java 1.5 Operating System Concepts – 7th edition, Jan 23, 2005 4.29 Silberschatz, Galvin and Gagne ©2005 Thread-Specific Data Allows each thread to have its own copy of data Useful when you do not have control over the thread creation process (i.e., when using a thread pool) Operating System Concepts – 7th edition, Jan 23, 2005 4.30 Silberschatz, Galvin and Gagne ©2005 Scheduler Activations Both M:M and Two-level models require communication to maintain the appropriate number of kernel threads allocated to the application Scheduler activations provide upcalls - a communication mechanism from the kernel to the thread library An intermediate data structure called LWP (Lightweight Process) between user thread and kernel thread This communication allows an application to maintain the correct number of kernel threads Operating System Concepts – 7th edition, Jan 23, 2005 4.31 Silberschatz, Galvin and Gagne ©2005 Operating System Examples Windows XP Threads Linux Threads Operating System Concepts – 7th edition, Jan 23, 2005 4.32 Silberschatz, Galvin and Gagne ©2005 Windows XP Threads Implements the one-to-one mapping Each thread contains A thread id Register set Separate user and kernel stacks Private data storage area Context of the threads The primary data structures of a thread include: ETHREAD (executive thread block) KTHREAD (kernel thread block) TEB (thread environment block) Operating System Concepts – 7th edition, Jan 23, 2005 4.33 Silberschatz, Galvin and Gagne ©2005 Windows XP Threads Operating System Concepts – 7th edition, Jan 23, 2005 4.34 Silberschatz, Galvin and Gagne ©2005 Linux Threads Linux refers to them as tasks rather than threads Thread creation is done through clone() system call clone() allows a child task to share the address space of the parent task (process) CLONE_FS, CLONE_VM, CLONE_SIGHAND, CLONE_FILES Operating System Concepts – 7th edition, Jan 23, 2005 4.35 Silberschatz, Galvin and Gagne ©2005 Linux Threads clone() system call Linux doesn’t distinguish between process and thread Operating System Concepts – 7th edition, Jan 23, 2005 4.36 Silberschatz, Galvin and Gagne ©2005 Java Thread States Operating System Concepts – 7th edition, Jan 23, 2005 4.37 Silberschatz, Galvin and Gagne ©2005 Pthread Example #include <pthread.h> … int main(int argc, char *argv[]) { pthread_t tid; pthread_attr_t attr; … pthread_attr_init(&attr); pthread_create(&tid, &attr, runner, argv[1]); pthread_join(tid, NULL); … } void *runner(void *param) { … pthread_exit(0); } Operating System Concepts – 7th edition, Jan 23, 2005 4.38 Silberschatz, Galvin and Gagne ©2005 Win32 Thread Example #include <windows.h> … DWORD WINAPI Summation(LPVOID Param) {… } int main(int argc, char *argv[]) { DWORD ThreadId; HANDLE ThreadHandle; … ThreadHandle = CreateThread(NULL, 0, Summation, &Param, 0, &ThreadId); if (ThreadHandle !=NULL) { WaitForSingleObject(ThreadHandle, INFINITE); CloseHandle(ThreadHandle); … } Operating System Concepts – 7th edition, Jan 23, 2005 4.39 Silberschatz, Galvin and Gagne ©2005 Java Thread Example Class Summation implements Runnable { … } public class Driver { public static void main() { … Thread thrd = new Thread(new Summation(upper, sumObject)); thrd.start(); try { thrd.join(); … } catch (InterruptedException ie) {} … } Operating System Concepts – 7th edition, Jan 23, 2005 4.40 Silberschatz, Galvin and Gagne ©2005 End of Chapter 4