The remainder of this article, I will refer to user space threadsĪs fibers, and kernel threads as threads. Sometimes, user space threads are calledįibers, to suggest that they are "lighter" than kernel threads. However, the cost is less than an operating When this is done in user space, there is still a penaltyįor a context switch. Library or program is responsable for scheduling and executing Of various multitasking approaches with respect to web servers. Research project has an excellent analysis of the performance This is the reason that single threaded web servers, like thttpd, performīetter than multi-threaded web servers, like Apache. Than a single thread which distributes its time between different Therefore, many simultaneous threads will be slower Is a penalty due to the overhead of saving and restoring the state Operating system switches between threads, a context switch, there The disadvantage of kernel threads is that each time the In multiprocessor computers, which can be an enormous performance System to schedule different threads to run on different processors Which means that the scheduling of which process is supposed to run Modern operating systems directly support threads in the kernel, Taken to avoid problems where two threads try to access a shared Way, if a shared resource is modified in one thread, the change is The concept is that a single processĬan have a number of threads, and everything is shared between themĮxcept the execution context (the stack and CPU registers). Threads were created to make this sort of resource
Resources to be shared between them, the model quickly becomesĬumbersome. However, if there are many processes and many Inter-process communication is simple and easy to use when it is Operating system routines for inter-process communication (IPC),įigure 1: Linux System Process List Threads For example,Ĭurrently running on my Linux system, and there are four processesĮxecuting mozilla-bin. That many processes can belong to a single program. ItĪlso keeps each process seperate, preventing one process from The operating system sharesĬomputing resources between all the processes that are running. ProcessesĮach program is a seperate process. Multitasking provided by the operating system.
In traditional operating systems, there are two tools for Of knowledge about C and the Linux kernel, I went out to build my However, I wasĬurious about how threads actually work.
Of thread library, such as standard Posix threads. All modern operating systems supply some sort Threads allow multiple parts of a program to Processing, and web servers must be able to send information to Repaint the display and respond to user input while doing any There are many programs which must be able
When a program is executed on a computer, it is executed a lineĪt a time, which each line containing a command to execute, orĭirections about which piece of code to execute next.