Translation lookaside buffer consistency: a software approach

We discuss the translation lookaside buffer (TLB) consistency prob-lem for multiprocessors, and introduce the Mach shootdown algo-rithm for maintaining TLJ3 consistency in software. This algorithm has been implemented on several multiprocessors, and is in regular production use. Performance evaluations establish the basic costs of the algorithm and show that it has minimal impact on applica-tion performance. As a result, TLB consistency does not pose an insurmountable obstacle to multiprocessors with several hundred processors. We also discuss hardware support options for TLB consistency ranging from a minor interrupt structure modification to complete hardware implementations. Features are identified in current hardware that compound the TLB consistency problem; re-moval or correction of these features can simplify and/or reduce the overhead of maintaining TLB consistency in software.