Profile-directed restructuring of operating system code
IBM Systems Journal
In this paper we describe how a profiling system can be successfully used to restructure the components of an operating system for improved overall performance. We discuss our choice of a profiling system and how it was agplied to the AS1400 (Application System1400 ) operating system for the purpose of reordering code. Previous work in the industry has been mainly useful only for application programs. Our work demonstrates how such techniques can be applied to operating system code, while
... ving maintainability of the operating system in the customer's environment. Wopyright 1998 by International Business Machines Corporation. Copying in printed form for private use is permitted without payment of royalty provided that (1) each reproduction is done without alteration and (2) the Journal reference and IBM copyright notice are included on the first page. The title and abstract, but no other portions, of this paper may be copied or distributed royalty free without further permission by computer-based and other information-service systems. Permission to republish any other portion of this paper must be obtained from the Editor. 270 SCHMIDT ET AL. 0018-8670/98/5500 0 1998 IEM IBM SYSTEMS JOURNAL, VOL 37, NO 2, 1998 Contributions of this paper. Aware of the performance benefits achieved using FDPR on other platforms within IBM, we began to consider how this technology could be used to improve performance on the Application System/4OO* (~s i 4 0 0 * ) PowerPc AS*-based computer systems. We also wanted to take things a step further: Rather than just applying this technology to applications, our goal was to improve the performance of the ASI400 operating system. We are not aware of any previous attempt to ship an operating system that has been reordered in this manner. (Experiments with reordering operatingsystem kernels have been d e s~r i b e d ,~~.~~ but to our knowledge these techniques have not been used in products that have been shipped to customers.) SCHMIDT ET AL.