Reducing Memory Traffic with Approximate Compression
Licentiate thesis, 2020

Memory bandwidth is a critical resource in modern systems and has an increasing demand. The large number of on-chip cores and specialized accelerators improves the potential processing throughput but also calls for higher data rates. In addition, new emerging data-intensive applications further increase memory traffic. On the other hand, memory bandwidth is pin limited and power constrained and is therefore more difficult to scale. This thesis proposes lossy memory compression as a means to reduce data volumes by exploiting the ability of applications to tolerate approximations in parts of their datasets. A reduction of off-chip memory traffic leads to reduced memory latency, which in turn improves the performance and energy efficiency of the system. The first part of this thesis introduces Approximate Value Reconstruction (AVR), which combines a low-complexity downsampling compressor with an LLC design able to co-locate compressed and uncompressed data. Two separate thresholds are employed to limit the error introduced by approximation. For applications that tolerate aggressive approximation in large fractions of their data, AVR reduces memory traffic by up to 70%, execution time by up to 55%, and energy costs by up to 20% introducing up to 1.2% error to the application output. The second part of this thesis proposes Memory Squeeze (MemSZ), introducing a parallelized implementation of the more advanced Squeeze (SZ) compression method. Furthermore, MemSZ improves on the error limiting capability of AVR by keeping track of life-time accumulated error. An alternate memory compression architecture is also proposed, which utilizes 3D-stacked DRAM as a last-level cache. MemSZ improves execution time, energy and memory traffic over AVR by up to 15%, 9%, and 64%, respectively.

Memory Compression

Memory Systems

Compression

Computer Architecture

Lossy Compression

Approximate Computing

Opponent: Georgios I. Goumas, National Technical University of Athens, Greece

Author

Albin Eldstål-Ahrens

Chalmers, Computer Science and Engineering (Chalmers), Computer Engineering (Chalmers)

AVR: Reducing Memory Traffic with Approximate Value Reconstruction

ACM International Conference Proceeding Series,;Vol. 5 August 2019(2019)

Paper in proceeding

Eldstål-Ahrens, A and Sourdis, I. MemSZ: Squeezing Memory Traffic with Lossy Compression

ACE: Approximate Algorithms and Computing Systems

Swedish Research Council (VR) (2014-6221), 2015-01-01 -- 2018-12-31.

Subject Categories

Computer Engineering

Embedded Systems

Computer Systems

Areas of Advance

Information and Communication Technology

Infrastructure

C3SE (Chalmers Centre for Computational Science and Engineering)

Publisher

Chalmers

Online

Opponent: Georgios I. Goumas, National Technical University of Athens, Greece

More information

Latest update

6/5/2020 1