[$] Modernizing swapping: virtual swap spaces

The kernel’s unloved but performance-critical swapping subsystem has been
undergoing multiple rounds of improvement in recent times. Recent articles
have described the addition of the swap
table as a new way of representing the state of the swap cache, and the removal of the swap map as the way of
tracking swap space. Work in this area is not done, though; this series from
Nhat Pham addresses a number of swap-related problems by replacing the
new swap table structures with a single, virtual swap space.