Delegation with Trust: A Scalable, Type- and Memory-Safe Alternative to Locks

Abstract

We present Trust, a general, type- and memory-safe alternative to locking in concurrent programs. Instead of synchronizing multi-threaded access to an object of type T with a lock, the programmer may place the object in a Trust. The object is then no longer directly accessible. Instead a designated thread, the object's trustee, is responsible for applying any requested operations to the object, as requested via the Trust API. Locking is often said to offer a limited throughput per lock. Trust is based on delegation, a message-passing technique which does not suffer this per-lock limitation. Instead, per-object throughput is limited by the capacity of the object's trustee, which is typically considerably higher. Our evaluation shows Trust consistently and considerably outperforming locking where lock contention exists, with up to 22x higher throughput in microbenchmarks, and 5-9x for a home grown key-value store, as well as memcached, in situations with high lock contention. Moreover, Trust is competitive with locks even in the absence of lock contention.