[X4U] Having Windows open drain resources?

[Ed Gould]

On Apr 7, 2009, at 5:43 AM, David Ledger wrote:

> At 18:41 -0500 5/4/09, Ed Gould wrote:
>> Zap:
>>
>> This is a general questions for all operating systems. It really  
>> depends on the OS (for VM) . There is not hard and fast answer as  
>> (IIRC) it depends on how the OS "polls" (looks to see if there is  
>> something to do) AND how the VM handles paging. IIRC the VM for  
>> PC's is immature and not great for paging where as other OS's semi  
>> talk to VM and let VM carry out the paging . Since the VM version 
>> (for PC's) is not sophisticated  I would suspect that there is  
>> essentially double page ins and the same for pageouts(this is only  
>> a guess).
>> Bottom line it depends on the OS.
>
> The VM PCs use isn't really relevant. The way VM is done on Unix is  
> fairly well known at different time frames. What OS X uses may not  
> be a sophisticated as in HP-UX (say), but not far off.
>
> David
>

David:

I disagree. Double paging is bad and especially in small computer  
land as I/O is sooooo slow and the inability to chain I/O requests  
(so that say 20 I/O operations get done but with only one trip  
thought the code to do I/O). I have worked on systems that do a  
"handshake" between the OS and VM so VM does the paging it is a  
really nice and time saving feature. Some OS's know that they are  
running under VM and do this automatically others you have to tell  
them (each OS does it slightly differently).

Ed