What is priority setting?

Answer 1

In computer Assuming this is from the windows taskmanager:

the priority setting is Input Output interrupts, this setting determines how often the processor should update the activities of this application, the higher this setting the more often the processor in the PC updates information regarding this application, and the less time it spends on other applications, typically this setting should be left alone, as misusing it can have consequences can result in crashing the program or the operating system which will simply require a reboot.

If priority is set too high, especially if set too high for a application that is demanding or allows very few or limited interruptions can result in even the keyboard and mouse locking up

however setting a process priority is not all bad, sometimes when multi tasking advanced users who multitask many intensive tasks may need to set this.

Setting realtime priority is not recommended, as giving a task realtime priority may cause the task to use all processor resources

depending on the version of operating system you use a set priority may be handled different ways, some operating systems realtime priority results in higher priority than drives, in other systems it doesn't however, having a higher priority level than the kernel or drivers can result in instability for drivers, your application, and the operating system and input devices

realtime priority however is not totally useless, properly written applications that can have realtime priority set can handle being run in this mode, however it should be used with caution as it can have many unexpected results

applications given kernal level priorities such as realtime also, are not allowed to use virtual memory and swapfile which can be beneficial or hazardous to your use experience, as this will limit memory available to other applications, but can greatly improve performance by preventing the application from going into swapfile when your system runs out of memory and will result in pushing other applications into swapfile, if you absolutely need to prevent your application from lagging doing this may help, but also may greatly hinder the performance of other applications and may cause your application to run out of memory in scenarios where it normally wouldn't

generally application priority settings are best left alone unless there is a need, also using this as a performance booster typically does not result in a noticeable improvement of performance unless you use realtime mode, which can however have severe negative impacts on the app its set to other applications or the operating system, its something best avoided unless necessary as the performance gain is generally not worth the stability trade off unless your absolutely sure of the effect.

an example of where process priority can be useful and the negative trade off:

when using some applications such as games in some cases if you notice the game is sluggish and the hard drive is thrashing this is oftentimes because other applications are automatically receiving higher priority and using the memory and processor resources first, setting a higher priority can smooth out performance by putting the game first on process scheduling, however may degrade performance or crash other applications. some extremely intensive 3D games that can swallow multiple GB of memory can have performance issues with memory and other applications smoothed out by setting priority higher, however when this is the case, generally your best off closing the other applications and leaving priority as is. a PC that runs a specific game might get 2-3 FPS while running that game, and may get 3-5 by running in realtime priority however, the trade off might be losing mouse and keyboard control and being required to reboot the computer by powering off during run.