sutton036

Since the 1950s there have been three main families of collectors: semi-space, mark-sweep and mark-compact. Almost all production GCs have been generational mark-sweep even though they exhibit pathological performance when the nursery is full of survivors because they are marked, (physically) copied and all references to them updated which is ~3x slower than necessary and is practically useful when filling a hash table with heap-allocated keys and/or values. The Beltway (2002) and Immix (2008) garbage collectors introduced the new family called the mark-region GCs. With a mark-region GC the entire heap is a collection of regions and so is the nursery generation so it can be logically aged by replacing it with another region when it is full of survivors. Sun's Hotspot JVM introduced the first mainstream mark-region GC with its G1 collector. The advent of multicore in 2005 has meant more emphasis on parallel and concurrent garbage collectors. The Staccato (2008) garbage collector ...

A new retail financial trading platform called LMAX recently published their work on new software technology for low-latency servers that they call the "disruptor": We have noticed a striking similiarity between their disruptor and an old garbage collection algorithm from 1992 called Baker's Treadmill : The LMAX disruptor and the story behind it are very interesting in their own right and well worth reading up on. In their system, binary messages come from the "receiver" and are distributed to the "journaller", "replicator" and "unmarshaller" in parallel and the "unmarshaller" then passes on the deserialized messages to the "consumer". The core of their idea is to accomplish all of this message passing using a single shared data structure, the disruptor, rather than using several separate concurrent queues. Baker's Treadmill is a low-latency garbage collection algorithm. Allocated blocks in the heap are li...