prefaulting MAP_ANONYMOUS pages

I am trying to optimize a malloc-based benchmark that is mmapping anonymous memory (via mmap) and then eventually taking a page fault on every page that was allocated. This is pretty inefficient for two reasons:

1) Lots of page faults, which drop performance by a factor of 10 compared to the case where everything is faulted in.

2) Lack of concurrency when faulting from multiple threads on the same object (it is basically serialized, so no benefits from multiple CPUs)

I think a better way to go might be to do prefetching to reduce the number of page faults. We do this for other types of mappings, but apparently not for anonymous mmapped memory. I am still trying to get my head around the code here, but it looks like vm_fault_prefault is going to return without doing anything because of

while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
...

/*
* give-up when a page is not in memory
*/

Also vm_fault_additional_pages() isn't getting called because TRYPAGER returns false for default objects.

Is there a way to achieve this that I am overlooking? If not can someone give me some advice about what is needed?

Kris
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