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Abstract : |
Multimodel multiprocessors provide both shared memory and message passing primitives to the user for efficient communication. In a multiuser machine, translation permits machine resources to be virtualized and protection permits users to be isolated. The challenge in a multiuser multiprocessor is to provide translation and protection sufficient for general-purpose computing without compromising communication performance, particularly the performance of communication between parallel threads belonging to the same computation. FUGU is a proposed architecture that integrates translation and protection with a set of communication mechanisms originally designed for high performance on a single-user, physically-addressed, large-scale, multimodel multiprocessor. Communication in FUGU is based on the mechanisms of the Alewife machine [1]. The mechanisms are shared memory with hardware cache coherence, user-level message sends and receives, and a user-controlledDMA facilityintegrated with messages for bulk transfers. This paper presents a design that integrates translation and protection with these communication mechanisms. Three components of the design are novel. First, we propose maintaining TLB coherence as a side-effect of cache coherence on page table entries. Second, we describe how to permit user-launched and user-handled messages without dedicating physical memory for buffering at the sender or at the receiver. We propose to use a rudimentary, second, system-only network to avoid deadlock of the user-accessible network. Third, we show how to integrate user DMA with virtual memory to permit bulk transfers without prenegotiation and global locking of physical memory., |
