added the new feature in linux2.6.28
Systems with a lot of memory have lots (millions) of pages. When the
replacement algorithm has to search candidate pages to be swapped, it
has to search between all the pages, and in big systems this can take
too much time. In 2.6.28, the file-backed pages (pages that belong to
some file on the disk) and the anonymous pages (pages that are not part
of any file, like ie. pages obtained with malloc, which need to be
written to swap before being evicted) are put in two different lists,
unlike previous releases, that used a single list. The algorithms can
decide to look into only one of those lists without needing to look in
the other. Additionally, there're pages that cannot be deleted from
memory, for example because they're mlock()'ed, or because they belong
to a ramfs filesystem. Those pages are put into a special third list,
which won't be searched at all by the algorithms because they can not
be evicted.
it also rewrite the vmap layer.
the detail refer to :
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