TurboTag: lookup filtering to reduce coherence directory power

On-chip coherence directories of today's multi-core systems are not energy efficient. Coherence directories dissipate a significant fraction of their power on unnecessary lookups when running commercial server and scientific workloads. These workloads have large working sets that are beyond the reach of on-chip caches of modern processors. Limited to capturing a small part of the working set, private caches retain cache blocks only for a short period of time before replacing them with new blocks. Moreover, coherence enforcement is a known performance bottleneck of multi-threaded software, hence data-sharing in optimized highperformance software is minimal. Consequently, the majority of the accesses to the coherence directory find no sharers in the directory because the data are not available in the on-chip private caches, effectively wasting power on the coherence checks. To improve energy-efficiency for future many-core systems, we propose TurboTag, a filtering mechanism to elim...

• Type: Conference
• Year: 2010
• Where: ISLPED
• Authors: Pejman Lotfi-Kamran, Michael Ferdman, Daniel Crisan, Babak Falsafi
• Keywords: Coherence Directories, Hardware, ISLPED 2010, On-chip Coherence Directories, Working Set