Subject: free page allocation in Netbsd
To: None <tech-kern@NetBSD.ORG>
List: tech-kern
Date: 12/29/1996 14:29:49
 Hi , 
	Today I was comparing the vm_page_alloc ( the routine that actually  
allocates free physical pages from the free list) of netbsd and freebsd, in  
freebsd the vm_page_alloc routine has three types of requests VM_PAGE_NORMAL,  
VM_ALLOC_SYSTEM, VM_ALLOC_INTERRUPT, depending on the # of free pages left in  
the system it satisfies the requests, ie. in effect it always keeps some pages  
for VM_ALLOC_INTERRUPT types of requests, I think that it is a neat way of  
allocating a page, in netbsd if a system is under heavy memory load and the #  
of free pages at any point drop to zero, then the memory requests from the  
interrupt routines cannot be satisfied, so in these conditions system can hang. 

Harish Singh Rawat			   E-Mail : 
Oracle Software India. Ltd.            Voice  : +91 (80) 225 - 6098/6099 
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