Concurrent Pagecache

Overview

This paper presents a concurrent pagecache for Linux, which is a continuation of the existing lockless pagecache. Currently the pagecache is protected by a reader/writer lock. The lockless pagecache work focuses on removing the reader lock, however, this paper presents a method to break the write side of the lock. Firstly, since the pagecache is centered around the radix tree, it is necessary to alter the radix tree in order to support concurrent modifications of the data structure. Secondly, pagecache is adapted, by removing all non-radix tree consumers of the lock's protection, and extend the pageflag, introduced by the lockless pagecache, into a second per page lock.