 
Summary: Page Replacement for General Caching Problems
Susanne Albers Sanjeev Arora y
Sanjeev Khannaz
Abstract
Caching (paging) is a wellstudied problem in online al
gorithms, usually studied under the assumption that all
pages have a uniform size and a uniform fault cost (uni
form caching). However, recent applications related to the
web involve situations in which pages can be of di erent
sizes and costs. This general caching problem seems more
intricate than the uniform version. In particular, the of
ine case itself is NPhard. Only a few results exist for the
general caching problem 8, 17]. This paper seeks to de
velop good o ine page replacement policies for the general
caching problem, with the hope that any insight gained here
may lead to good online algorithms. Our rst main result
is that by using only a small amount of additional mem
ory, say O(1) times the largest page size, we can obtain an
O(1)approximation to the general caching problem. Note
that the largest page size is typically a very small fraction
