|
nice (IPA pronunciation: /naɪs/) is a command found on UNIX and other POSIX-like operating systems such as Linux. nice directly maps to a kernel call of the same name. For a given process, it changes the priority in the kernel's scheduler. A nice value of −20 is the highest priority and 19 is the lowest priority. The default nice value for most processes is 0. For information on how to read IPA transcriptions of English words see here. ...
Unix or UNIX is a computer operating system originally developed in the 1960s and 1970s by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie, and Douglas McIlroy. ...
To meet Wikipedias quality standards, this article or section may require cleanup. ...
To meet Wikipedias quality standards, this article or section may require cleanup. ...
Linux (also known as GNU/Linux) is a Unix-like computer operating system. ...
A kernel connects the software and hardware of a computer. ...
In computing, a process is a running instance of a program, including all variables and other states. ...
A priority queue is an ADT (abstract data type) supporting the following two operations: add an element to the queue with an associated priority remove the element from the queue that has the highest priority, and return it The simplest way to implement a priority queue data type is to...
Scheduling is a key concept in computer multitasking and multiprocessing operating system design, and in real-time operating system design. ...
Nice becomes useful when several processes are demanding more resources than the CPU can provide. In this state, a higher priority process will get a larger chunk of the CPU time than a lower priority process. If the CPU can deliver more resources than the processes are requesting, then even the lowest priority process can get up to 99% of the CPU. Only the superuser (root) may set the nice value to a negative (higher priority) value. CPU redirects here. ...
On many computer operating systems, superuser is the term used for the special user account that is controlled by the system administrator. ...
There is also a renice command, which is used to change the priority of a process that's already running.
The exact mathematical effect of setting a particular niceness value for a process depends on the details of how the scheduler is designed on that implementation of unix. A particular operating system's scheduler will also have various heuristics built into it, e.g., to favor processes that are mostly I/O-bound over processes that are CPU-bound. As a simple example, however, when two otherwise identical CPU-bound processes are running simultaneously on a single-CPU Linux system, each one's share of the CPU time will be proportional to 20-p, where p is the process's priority. Thus a process run with nice -15 will receive 1/4 of the CPU time allocated to a normal-priority process: (20-15)/(20-0)=1/4. On the BSD 4.x scheduler, on the other hand, the ratio in the same example is more like ten to one.
Language bindings
C nice getpriority(2)
Perl use POSIX (); POSIX::nice(7); # like the renice shell command; increase niceness level by 7 my $prio = getpriority(0,0); # like the C function
See also
The GNU Core Utilities or coreutils is a package of GNU software containing many of the basic tools such as cat, ls, and rm needed for Unix-like operating systems. ...
Wikibooks has more about this subject: kill In Unix and Unix-like operating systems, kill is a command used to send simple messages to processes running on the system. ...
To meet Wikipedias quality standards, this article or section may require cleanup. ...
External link |
Feeds |
Contact