ObjecTier: Non-Invasively Boosting Memory Tiering Performance

Abstract

Recent research has developed page-based memory-tiering systems that place hot pages in fast tiers and cold pages in slower, more capacious tiers. However, applications place many objects together within pages, and most pages contain some objects that are hot and some that are cold. Our simulations of a key-value workload confirm this; even the hottest pages in the fast tier can contain 50% cold data. To improve fast tier utilization, we describe the design of a new framework, ObjecTier, that uses application knowledge to efficiently consolidate hot data and cold data. This allows ObjecTier-enabled applications to boost fast tier hit rates and improve performance regardless of which underlying memory tiering system they use underneath, even if that system is page based. With simulations, we show that ObjecTier may improve average memory access time (AMAT) by 2× without adding any memory space overhead for our simulated key-value store workload. We conclude by outlining the next steps to make the ObjecTier framework a reality for easy adaptation of applications like key-value stores and other indexed databases.