• Simplify vm_pageout_scan() by introducing a new vm_pageout_clean() function that does the locking and validation associated with cleaning a page. This moves 150 lines of code into its own function.
• Rename vm_pageout_clean() to vm_pageout_cluster() to define what it really does; clustering nearby pages for pageout optimization.

Reviewd by: alc, kib, kmacy
Tested by: pho (earlier version)
Sponsored by: EMC / Isilon