Windows NT processor scheduling: Difference between revisions

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{{OrphanOne source|date=November 20062022}}

Without '''Windows NT processor scheduling''' refers to the process by which [[MicroprocessorWindows NT]] woulddetermines givewhich attentionjob to(task) jobsshould basedbe run on whenthe they[[Central arrivedprocessing inunit|computer theprocessor]] queue.at which Thistime. is notWithout alwaysscheduling, optimal.the processor Somewould applicationsgive shouldattention beto givenjobs morebased timeon withwhen thethey processorarrived becausein thatthe programqueue, which is moreusually criticalnot optimal. As Inpart orderof tothe do thisscheduling, the processor givegives a priority level to different processes running on the machine. When two processes are requesting service at the same time, the processor performs the jobs for the one with the higher priority.

Without '''processor scheduling''' the [[Microprocessor]] would give attention to jobs based on when they arrived in the queue. This is not always optimal. Some applications should be given more time with the processor because that program is more critical. In order to do this, the processor give a priority level to different processes running on the machine. When two processes are requesting service at the same time, the processor performs the jobs for the one with the higher priority.

There are six named priority levels:

• *Realtime

• *High

• *Above Normal

• *Normal

• *Below Normal

• *Low

These levels have associated numbers with them. [[Application software|Applications]] start at a base priority level of eight. The system dynamically adjusts the priority level to give all applications access to the processor.

Priority levels 0 - 15 are used by dynamic applications. Anything running at a dynamic level can be written to the [[Windows NT]] Pagefile. This includes user application by default and operating system functions that are not imperative to the performance of the operating system. Priority levels 16- 31 are reserved for real-time applications that cannot be written to the Windows NT Pagefile. Because of this, they will not be paged to disk and will reside in main memory.

== Affinity ==

In a [[multiprocessing]] environment with more than one [[logical processor]] (i.e. [[multicore|multiple cores]] or [[hyperthreading]]), more than one task can be running at the same time. However, a process or a thread can be set to run on only a subset of the available logical processors. The Windows Task Manager utility offers a user interface for this at the process level.<ref>{{Cite book |title=Microsoft Windows internals : Microsoft Windows Server 2003, Windows XP, and Windows 2000 |last=Russinovich |first=Mark E. |date=2005 |publisher=Microsoft Press |last2=Solomon |first2=David A. |isbn=0735619174 |edition=4th |___location=Redmond, WA |oclc=57449950 |url-access=registration |url=https://archive.org/details/isbn_9780735619173 }}</ref>

==References==

{{reflistReflist}}

{{Windows Components}}

[[Category:Windows NT kernel]]

[[Category:SchedulingProcessor scheduling algorithms]]