On Wed, 1 May 2002, David Schultz wrote:
> Thus spake Lamont Granquist <[EMAIL PROTECTED]>:
> > Does the FreeBSD VM system do O(1) or O(N) searches for gaps in a
> > processes virtual memory space?
>
> I'm not a VM guru, but if I'm reading vm_map.c right, it's O(n)
> w.r.t. the number of map entries. But since map entries are merged
> when possible, I would expect the cost to stay fairly low.
I know of one app running on Linux/x86 which spends about 40% of its
kernel time in get_unmapped_pages() (the Linux equivalent). Trying to
mmap() bits and pieces of 20GB worth of data into a 4GB VM space tends to
lead to a lot of fragmentation. Be interesting to see if merging would
help, but I'd suggest an O(1) algorithm for this.
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