Analysis of the paging behavior of UNIX

Abstract

We analyze the paging behavior of several different versions of UNIX by recording traces of paging activity over time and writing programs to analyze the traces. We recorded periodic totals of paging events instead of individual paging events themselves. Our analysis shows that paging activity accounts for between 15% and 21% of all disk block accesses. Average paging system traffic is very low. The paging system is idle most of the time and paging activity occurs in large periodic bursts. Despite the fact that it is often overlooked, swap related paging accounts for a significant portion of all paging activity (between 24% and 71%). Furthermore, the behavior of swap-related paging differs greatly from the well-studied behavior of demand paging. The ratio of pages read to pages written (which varies between 0.85 and 1.9) is lower than typical read to write ratios for file system accesses. Paging activity is loosely correlated with load average or number of users.