A Cache-Based Hardware Accelerator for Memory Data Movements
Filipa Duarte · Research Repository (Delft University of Technology) · 2008
This dissertation presents a hardware accelerator that is able to accelerate large (including non-parallel) memory data movements, in particular memory copies, performed traditionally by the processors. As todays processors are tied with or have integrated caches with varying sizes (from several kilobytes in hand-held devices to many megabytes in desktop devices or large servers), it is only logical to assume that data to-be-copied by a memory copy is already present within the cache. This is especially true when considering that such data often must be processed first. This means that the presence of the caches can be utilized to significantly reduce the latencies associated with memory copies, when a smarter way to perform the memory copy operation is used. Therefore, the proposed accelerator for memory copies takes advantage of the presence of these caches and introduces a redirection mechanism that links the original data (in the cache) to the copied addresses (in a newly added indexing table). The proposed solutions avoid cache pollution and duplication of data, and efficiently schedule the access to the main memory, thus effectively reducing the latency associated with memory copies. Moreover, the proposed accelerator supports copies of cache line and word granularity, can be connected to a direct-mapped or a set-associative cache, and can efficiently reduce the memory copy bottleneck in single core processors and in multi-core processors that execute a message passing communication model. The proposed solutions have been implemented in a FPGA as a proof of concept and incorporated in a simulator running several benchmarks to determine the performance gains of the proposal. In particular, for the receiver side of the TCP/IP stack, the proposed solutions can reach speedups from 2.96 to 4.61 times and reduce the number of instructions executed by 26% to 44%.