GHC's Runtime System
summary
GHC’s runtime is described concretely: codegen exposes registers R1..R10 and special registers like CurrentTSO, allocation uses an Hp/HpLimit bump-pointer nursery (example: a 5-word / 40‑byte allocation), stacks use chunked Sp/SpLim regions, and the storage manager requests 1MB megablocks then slices into ~4KB blocks (can reserve ~1TB address space). The GC is generational with remembered sets; thunks use blackholing to indirections (eager vs lazy); schedulers use capabilities/tasks and TSOs with run queues and work‑pushing. Tooling: ThreadSanitizer, rr+gdb, Valgrind, +RTS flags; code pointers: InfoTables.h, Storage.c, HeapStackCheck.cmm, GC.c, Linker.c, utils/genapply; bytecode VM is a 16‑bit stack machine.
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chapters (15)
- 0:00GHC runtime intro
- 1:12Runtime overview
- 5:16STG machine recap
- 14:24Chunked stack
- 25:15Heap and nursery
- 32:55Closure types
- 43:23Thunk allocation
- 57:15Break recap
- 58:01Storage manager
- 1:00:32Megablock allocator
- 1:08:23Heap checks & GC
- 1:10:39Green threading
- 1:18:27Thread scheduler
- 1:23:08GHCi linker
- 1:26:47Debugging tools
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