Process - Revision history

Rice: /* Machine state */

2024-10-04T18:27:30Z

Machine state

← Older revision		Revision as of 18:27, 4 October 2024
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	* CPU [[Register\|registers]]		* CPU [[Register\|registers]]
	* The process [[stack]]		* The process [[stack]]
	* The address space		* The [[address space]]
	* etc.		* etc.

Rice: /* Process state */

2024-10-02T18:19:09Z

Process state

← Older revision		Revision as of 18:19, 2 October 2024
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	A process is '''scheduled''' when the OS moves it from Ready to Running. It is '''descheduled''' when it is moved from Running to Ready. This decision is made by the [[scheduler]].		A process is '''scheduled''' when the OS moves it from Ready to Running. It is '''descheduled''' when it is moved from Running to Ready. This decision is made by the [[scheduler]].

			The kernel also keeps a table of all the metadata of processes. This include PID, parent, page tables, etc.

	== Processes in Linux ==		== Processes in Linux ==

Rice at 17:53, 30 September 2024

2024-09-30T17:53:05Z

← Older revision		Revision as of 17:53, 30 September 2024
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	To run a new process, the ''exec'' syscall can be used. It replaces the current process with that specified in the arguments.		To run a new process, the ''exec'' syscall can be used. It replaces the current process with that specified in the arguments.

			== Motivation of ''fork'' ==
			The motivation behind this unintuitive set of APIs (fork, wait, exec) is to allow the parent process time to alter the environment of the child process.

	= Sources =		= Sources =

Rice: /* Processes in Linux */

2024-09-30T17:46:26Z

Processes in Linux

← Older revision		Revision as of 17:46, 30 September 2024
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	== Processes in Linux ==		== Processes in Linux ==

	~~===== Init process =====~~
	When the computer starts, the only thing the kernel execute in the [[user space]] is a init command (shown with ps -f 1). This process is allocated a PID of 1 and is the only process with no parent process.		When the computer starts, the only thing the kernel execute in the [[user space]] is a init command (shown with ps -f 1). This process is allocated a PID of 1 and is the only process with no parent process.

	~~===== Creating a process =====~~
	In contrast to the init process, all other processes are created by parent processes. This is done with ''fork'' and ''exec''. First, the [[shell]] will run ''fork'' to create a cloned process from the current process, and ''exec'' replaces the program in the cloned process with another program.		In contrast to the init process, all other processes are created by parent processes. This is done with ''fork'' and ''exec''. First, the [[shell]] will run ''fork'' to create a cloned process from the current process, and ''exec'' replaces the program in the cloned process with another program.

			The syscall ''fork'' clones a process almost perfectly. For example, the child process would not start running at ''main''; instead, it continues where the parent leaves off. The only differences between the two processes is the return value of ''fork'': In the parent it is the PID of the child, whereas in the child it is 0. This syscall is notably non-deterministic, as the CPU scheduler is free to run either process before the other.

			The ''wait'' syscall halt execution of the parent until the child is complete.

			To run a new process, the ''exec'' syscall can be used. It replaces the current process with that specified in the arguments.

	= Sources =		= Sources =

Rice at 18:17, 27 September 2024

2024-09-27T18:17:24Z

← Older revision		Revision as of 18:17, 27 September 2024
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	[[Category:Computer Science]]		[[Category:Computer Science]]
	A '''program''' is a passive set of machine code instructions and data stored in an executable image. A '''process''' can be thought of as this passive program in action. More formally, it is one or more threads in their own address space.		A '''program''' is a passive set of machine code instructions and data stored in an executable image. A '''process''' can be thought of as this passive program in action. More formally, it is one or more [[Thread\|threads]] in their own address space.

	Processes are independent separate tasks. If one process crashed, it will not affect any other processes. The end goal of processes is to achieve the illusion of having multiple CPUs when executing multiple programs. This is done by '''virtualization'''.		Processes are independent separate tasks. If one process crashed, it will not affect any other processes. The end goal of processes is to achieve the illusion of having multiple CPUs when executing multiple programs. This is done by '''virtualization'''.
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	* Linux processes, init, fork/exec, ps, kill, fg, bg, jobs: https://www.youtube.com/watch?v=TJzltwv7jJs		* Linux processes, init, fork/exec, ps, kill, fg, bg, jobs: https://www.youtube.com/watch?v=TJzltwv7jJs
	* Operating Systems, Three Easy Pieces		* Operating Systems, Three Easy Pieces
			[[Category:Operating System]]

Rice at 18:13, 27 September 2024

2024-09-27T18:13:24Z

← Older revision		Revision as of 18:13, 27 September 2024
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	[[Category:Computer Science]]		[[Category:Computer Science]]
	A '''program''' is a passive set of machine code instructions and data stored in an executable image. A '''process''' can be thought of as this passive program in action.		A '''program''' is a passive set of machine code instructions and data stored in an executable image. A '''process''' can be thought of as this passive program in action. More formally, it is one or more threads in their own address space.

	Processes are independent separate tasks. If one process crashed, it will not affect any other processes. The end goal of processes is to achieve the illusion of having multiple CPUs when executing multiple programs. This is done by '''virtualization'''.		Processes are independent separate tasks. If one process crashed, it will not affect any other processes. The end goal of processes is to achieve the illusion of having multiple CPUs when executing multiple programs. This is done by '''virtualization'''.

Rice at 05:10, 26 September 2024

2024-09-26T05:10:07Z

@@ Line 1: / Line 1: @@
 [[Category:Computer Science]]
-In Linux, a '''program''' is a passive set of machine code instructions and data stored in an executable image. A '''process''' can be thought of as this passive program in action.
+A '''program''' is a passive set of machine code instructions and data stored in an executable image. A '''process''' can be thought of as this passive program in action.
-Processes are independent separate tasks. If one process crashed, it will not affect any other processes.
+Processes are independent separate tasks. If one process crashed, it will not affect any other processes. The end goal of processes is to achieve the illusion of having multiple CPUs when executing multiple programs. This is done by '''virtualization'''.
-The kernel manages resource allocation (such as the CPU) between different processes. This is done by the [[scheduler]].
+== Machine state ==
 Representing the execution of a program, a process includes the state of the program first and foremost. This includes
@@ Line 12: / Line 10: @@
 * CPU [[Register|registers]]
 * The process [[stack]]
 Beyond the state of the program, each process is allocated its own process identifier (PID) and [[virtual memory]] among other things.
-== Lifetime of a process ==
+== Virtualization ==
 ===== Init process =====
@@ Line 27: / Line 57: @@
 * Linux documentation: https://tldp.org/LDP/tlk/tlk.html
 * Linux processes, init, fork/exec, ps, kill, fg, bg, jobs: https://www.youtube.com/watch?v=TJzltwv7jJs

Rice: Created page with "Category:Computer Science In Linux, a '''program''' is a passive set of machine code instructions and data stored in an executable image. A '''process''' can be thought of as this passive program in action. Processes are independent separate tasks. If one process crashed, it will not affect any other processes. The kernel manages resource allocation (such as the CPU) between different processes. This is done by the scheduler. == Process composition == Represen..."

2024-06-19T21:48:41Z

Created page with "Category:Computer Science In Linux, a '''program''' is a passive set of machine code instructions and data stored in an executable image. A '''process''' can be thought of as this passive program in action. Processes are independent separate tasks. If one process crashed, it will not affect any other processes. The kernel manages resource allocation (such as the CPU) between different processes. This is done by the scheduler. == Process composition == Represen..."

New page

[[Category:Computer Science]]
In Linux, a '''program''' is a passive set of machine code instructions and data stored in an executable image. A '''process''' can be thought of as this passive program in action.

Processes are independent separate tasks. If one process crashed, it will not affect any other processes.

The kernel manages resource allocation (such as the CPU) between different processes. This is done by the [[scheduler]].

== Process composition ==
Representing the execution of a program, a process includes the state of the program first and foremost. This includes

* The [[program counter]]
* CPU [[Register|registers]]
* The process [[stack]]

Beyond the state of the program, each process is allocated its own process identifier (PID) and [[virtual memory]] among other things.

== Lifetime of a process ==

===== Init process =====
When the computer starts, the only thing the kernel execute in the [[user space]] is a init command (shown with ps -f 1). This process is allocated a PID of 1 and is the only process with no parent process.

===== Creating a process =====
In contrast to the init process, all other processes are created by parent processes. This is done with ''fork'' and ''exec''. First, the [[shell]] will run ''fork'' to create a cloned process from the current process, and ''exec'' replaces the program in the cloned process with another program.

= Sources =

* Linux documentation: https://tldp.org/LDP/tlk/tlk.html
* Linux processes, init, fork/exec, ps, kill, fg, bg, jobs: https://www.youtube.com/watch?v=TJzltwv7jJs