The Susceptibility of Programs to Context Switching

AbstructModern memory systems are composed of several levels of caching. Design of these levels is largely an empirical practice. One highly-effective empirical method is the single-pass method wherein all caches in a broad design space are evaluated in one pass over the trace. Multiprogramming degrades memory system performance since (process) context switching reduces the effectiveness of cache memories. Few single-pass methods exist which account for multiprogramming effects. This paper uses a general model of single-pass algorithms, the recurrencdconflict model, and extends the model for recording the effects due to both voluntary context switches (e.& system calls) and involuntary context switches (e+, time quantum expiration). Involuntary context switches are modeled using the distribution of lengths between a reference to an address and the re-reference to the same address. The paper makes the assumptions that involunary context switches are equally likely to occur between each reference, and that one can independently estimate, f r -5 , the fraction of a cache’s contents flushed between context switches. The case where fc,s = 1 is used to measure the effect of worst-case context switch penalty (the susceptibility) of several members of the SPEC89 benchmark set to context switching. Some empirical results of frs are presented to illustrate the case where fc,. < 1. The model is validated against its assumptions by comparing its results with more-restrictive methods.