![]() ![]() Large objects are too expensive to move, so they are dealt with separately using a mark/sweep during a major collection.We need to track which objects are pinned, as we can not move those objects.The collection can be triggered by any thread.Must work with multi-threaded applications.The garbage collector is complicated by a number of issues: When the old generation is full as well, a major collection is performed. When the nursery is full, the collector will trigger a nursery collection, this is performed by the copying GC. Nursery collections reduce the amount of work required by the collector because usually there are few surviving objects that need to be copied, leaving lots of free space for subsequent allocations. All new objects are allocated in the nursery and during a collection the surviving objects are moved to the older generation memory block. The principle behind this two-stage collection (major and nursery) is based on the observation that many programs create a lot of short-lived objects that can be quickly collected. The collector distinguishes between two kinds of collections: major collections and nursery-collections which only operate on the current nursery. The garbage collector will trigger a collection when there is no space anymore in the memory already requested from the operating system. Pinned chunks, for objects that have been pinned-allocated.Old generations, where small objects are copied to. ![]() Large object store, where large objects are allocated.The nursery, where new small objects are allocated.Stop the world, meaning that during garbage collection, the program is stopped.Uses write barriers to minimize the work done on minor collections.Per-thread fragments for fast per-thread allocation.Mark and Sweep for the old generation and major collector.Mostly precise scanning (stacks and registers are scanned conservatively).In other words, all those objects are considered reachable, as well as those that they reference, and those that they reference, and so on. It considers as reachable objects those that are directly or indirectly referenced by the so-called “roots”, which are global variables, local variables on the stacks or in registers and other references explicitly registered as roots. It does that by discovering which objects might still be reached by the program and getting rid of the rest. The garbage collector, in short, is that part of the language’s or platform’s runtime that keeps a program from exhausting the computer’s memory, despite the lack of an explicit way to free objects that have been allocated. On macOS SGen provides several DTrace probes, described in the document SGen DTrace. The Benchmark Suite continuously runs benchmarks for each Mono revision to track performance regressions using CI. This garbage collector can be enabled by passing the –gc=sgen flag to Mono or if you are embedding Mono, by linking against the libmonosgen library instead of the libmono library. If you are interested on how to use SGen and how to tune it for your own application workloads, see the document Working With SGen.įor a few releases, Mono has shipped with a new garbage collector, we call this the SGen garbage collector. This document discusses the internals of SGen. ![]()
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