Bypass and insertion algorithms for exclusive last-level caches

Inclusive last-level caches (LLCs) waste precious silicon estate due to cross-level replication of cache blocks. As the industry moves toward cache hierarchies with larger inner levels, this wasted cache space leads to bigger performance losses compared to exclusive LLCs. However, exclusive LLCs make the design of replacement policies more challenging. While in an inclusive LLC a block can gather a filtered access history, this is not possible in an exclusive design because the block is de-allocated from the LLC on a hit. As a result, the popular least-recently-used replacement policy and its approximations are rendered ineffective and proper choice of insertion ages of cache blocks becomes even more important in exclusive designs. On the other hand, it is not necessary to fill every block into an exclusive LLC. This is known as selective cache bypassing and is not possible to implement in an inclusive LLC because that would violate inclusion. This paper explores insertion and bypa...

• Type: Journal
• Year: 2011
• Where: ISCA
• Authors: Jayesh Gaur, Mainak Chaudhuri, Sreenivas Subramoney
• Keywords: Driven Simulation, Hardware, ISCA 2011, Level Caches, Performance Losses