![]() ![]() The biggest chunk of time probably goes to copying the memory Obviously, this saves time.įor processes, there's a bit of copying to be done when fork is invoked, It tells the kernel there's no need to copy the virtual memory image, the openįiles, the signal handlers, and so on. When pthread_create passes all these CLONE_* flags, Since fork and pthread_create route to the same systemĬall in Linux, the difference would come from the differentįlags they pass in. Given the information presented earlier in the post, I would expect processĬreation to be somewhat more expensive than thread creation, but notĭramatically so. Sees the message the parent placed in buf, but whatever it writes intoīuf goes into its own copy and the parent can't see it. ![]() When called without the vm command-line argument, the CLONE_VMįlag is off, and the parent's virtual memory is copied into the child. This code sample passes a buffer into the child, and the child writes a string This is the only flag the sample passes into When the child terminates, which lets the parent use the plain wait call The SIGCHLD flag tells the kernel to send the SIGCHLD to the parent.The stack for the new task has to be allocated by the parent and passed into.There's also a raw system call which is discussed ![]() To threading APIs, and unlike the fork API. It takes a function pointer to the code the new task will run, similarly.Some things to note when clone is invoked: However, deep in the guts of these APIs and libraries,īoth processes and threads come into existence through a single Linux system Process-management APIs like fork, wait and so on. For application programmers, proceses and threads are created and Memory space processes, on the other hand, are tasks that don't share In Linux, threads are just tasks that share some resources, most notably their ![]() Main structure representing a task in the kernel is In kernel nomenclature this is called tasks (the Both are represented by the same data structuresĪnd scheduled similarly. What userspace sees as processes (the result of fork) and as threads (the In fact, for the Linux kernel itself there's absolutely no difference between Even the name "thread" suggests somethingĮxtremely lightweight compared to a heavy "process" - a mostly wrong intuition. Some programmers may have an outdated mental model about the difference between Due to variation between operating systems and the way OS courses are taught, ![]()
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December 2022
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