What is the realtime process priority setting for

Question

From what I ve read in the past  you re encouraged not to change the priority of your Windows applications programmatically  and if you do  you should never change them to  Realtime   What does the  Realtime  process priority setting do  compared to  High   and  Above Normal

User · Accepted Answer

A realtime priority thread can never be pre-empted by timer interrupts and runs at a higher priority than any other thread in the system. As such a CPU bound realtime priority thread can totally ruin a machine.

Creating realtime priority threads requires a privilege (SeIncreaseBasePriorityPrivilege) so it can only be done by administrative users.

For Vista and beyond, one option for applications that do require that they run at realtime priorities is to use the Multimedia Class Scheduler Service (MMCSS) and let it manage your threads priority. The MMCSS will prevent your application from using too much CPU time so you don't have to worry about tanking the machine.

User · Answer

Like all other answers before real time gives that program the utmost priority class  Nothing is processed until that program has been processed  On my pentium 4 machine I set minecraft to real time a lot since it increases the game performance a lot  and the system seems completely stable  so realtime isn t as bad as it seems  just if you have a multi-core set a program s affinity to a specific core or cores  just not all of them  just to let everything else be able to run in case the real time set programs gets hung up  and set the priority to real time

User · Answer

It basically is higher greater in everything else  A keyboard is less of a priority than the real time process  This means the process will be taken into account faster then keyboard and if it can t handle that  then your keyboard is slowed

User · Answer

Once Windows learns a program uses higher than normal priority it seems like it limits the priority on the process    Setting the priority from IDLE to REALTIME does NOT change the CPU usage   I found on My multi-processor AMD CPU that if I drop one of the CPUs ot like the LAST one the CPU usage will MAX OUT and the last CPU remains idle    The processor speed increases to 75  on my Quad AMD    Use Task Manager- select process- Right Click on the process- Select- Set Affinity Click all but the last processor  The CPU usage will increase to the MAX on the remaining processors and Frame counts if processing video will increase

User · Answer

Simply  the  Real Time  priority class is higher than  High  priority class  I don t think there s much more to it than that   Oh yeah - you have to have the SeIncreaseBasePriorityPrivilege to put a thread into the Real Time class   Windows will sometimes boost the priority of a thread for various reasons  but it won t boost the priority of a thread into another priority class   It also won t boost the priority of threads in the real-time priority class   So a High priority thread won t get any automatic temporary boost into the Real Time priority class   Russinovich s  Inside Windows  chapter on how Windows handles priorities is a great resource for learning how this works    http   web archive org web 20140909124652 http   download microsoft com download 5 b 3 5b38800c-ba6e-4023-9078-6e9ce2383e65 C06X1116607 pdf   Note that there s absolutely no problem with a thread having a Real-time priority on a normal Windows system - they aren t necessarily for special processes running on dedicatd machines   I imagine that multimedia drivers and or processes might need threads with a real-time priority   However  such a thread should not require much CPU - it should be blocking most of the time in order for normal system events to get processing

User · Answer

Real-time is the highest priority class available to a process  Therefore  it is different from  High  in that it s one step greater  and  Above Normal  in that it s two steps greater   Similarly  real-time is also a thread priority level   The process priority class raises or lowers all effective thread priorities in the process and is therefore considered the  base priority    So  a process has a    Base process priority class  Individual thread priorities  offsets of the base priority class    Since real-time is supposed to be reserved for applications that absolutely must pre-empt other running processes  there is a special security privilege to protect against haphazard use of it  This is defined by the security policy   In NT6   Vista    use of the Vista Multimedia Class Scheduler is the proper way to achieve real-time operations in what is not a real-time OS  It works  for the most part  though is not perfect since the OS isn t designed for real-time operations   Microsoft considers this priority very dangerous  rightly so  No application should use it except in very specialized circumstances  and even then try to limit its use to temporary needs

User · Answer

It would be the highest available priority setting  and would usually only be used on box that was dedicated to running that specific program   It s actually high enough that it could cause starvation of the keyboard and mouse threads to the extent that they become unresponsive   So basicly  if you have to ask  don t use it

[windows] What is the 'realtime' process priority setting for?

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