An FPGA-based Coprocessor for Hash Unit Acceleration

In recent times, applications like web-based search, antivirus scanners, cloud computing, social media applications, and network applications are extremely common. The hash table is a heavily used data structure in such applications. Modern microprocessors have several special function units (SFUs) such as a floating point unit, a memory management unit, and a cryptography unit. However, hashing is typically performed in software, which reduces the performance of such applications. In this paper, we propose an FPGA-based implementation of a hash unit (a hash function and a hash table) in an FPGA. The FPGA-based hash unit is implemented as a coprocessor for a CPU. The CPU and the FPGA communicate through a PCI Express (PCIe) interface. The hash table in our hash unit is implemented as a content-addressable memory (CAM), to enhance the speed of hash operations. The hash unit (HU) coprocessor is tested in the context of virus checking application, when the hashing operation only requires membership checks. Our HU can be used in other hashing applications as well; we use virus checking as a representative application. Hashing operations are performed in a batch on the FPGA, to provide better utilization of the PCIe bus. We demonstrate a significant performance of up to 7.3x for our FPGAbased hash unit implementation compared to a software-based hashing implementation. This speedup is for the entire virus checking application (not just the hash lookup portion of the virus checking application).