[X4U] how to view "pageouts?"

[Ed Gould]

On Jun 19, 2008, at 11:47 AM, David Ledger wrote:
> --------------------- 
> SNIP----------------------------------------------------------
> Other than memory mapped file I/O I'd be interested to know what  
> these other reasons are.
>
> David
>
>
The one or two that come to the top of my mind (there are others of  
course) are 1. The application tells the OS that the page will not be  
used in quite a long time (perhaps an error routine that is never(?)  
to be invoked) 2. The OS sees a wait issued by the application and  
due to other issues (like cpu busy, etc) decided to swap the entire  
application out. Some of the types of wait are either I/O and or  
waiting on input from the user. If the system is overloaded say by  
cpu usage then the system looks at the the applications that are not  
doing anything and frees up memory by swapping those applications out  
or another reason is that the OS keeps track of a a "routine"  and if  
its no longer in use it it moves it to the ready "que" to be paged  
out que and so long as the use count does not go up by the time its  
ready to be paged it is paged out or depending on how the OS is  
written  maybe just the page is freed and when the routine is need  
again it is paged in from the swap file, again it depends on how  
sophisticated the OS is.   It maybe just because the application says  
I am stopped and can go no further until an external event occurs  
like a time expiring at say 2 hours later(ICAL might be an example  
here). The MAC internals on scheduling is not externally published so  
there may be others as well, its difficult to say what was  
architected into the OS do I can only guess based on how other  
systems that *ARE* externalized.

I posted a lengthy pageout response yesterday and it was held for  
length restrictions. Maybe that will answer the question as well.

Ed