41.4.1 PagePool/Math

This is the simplest type of page pool. It has only one page, whose size can be generated by a given random variable. Page modification sequence and request sequence are generated using two given random variables. It has the following OTcl methods:

rX gen-pageid & Returns the page ID which will be requested next. Because it has only one page, it always returns 0.

gen-size & Returns the size of the page. It can be generated by a given random variable.

gen-modtime pageID mt & Returns the next modification time of the page. mt gives the last modification time. It uses the lifetime random variable.

ranvar-age rv & Set the file lifetime random variable as rv.

ranvar-size rv & Set the file size random variable to be rv.

NOTE: There are two ways to generate a request sequence. With all page pools except PagePool/ProxyTrace, request sequence is generated with a random variable which describes the request interval, and the gen-pageid method of other page pools gives the page ID of the next request. PagePool/ProxyTrace loads the request stream during initialization phase, so it does not need a random variable for request interval; see its description below.

An example of using PagePool/Math is at Section 41.8. That script is also available at ns/tcl/ex/simple-webcache.tcl.

Tom Henderson 2011-11-05