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Update performance.md

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Arseny Kapoulkine 2021-09-15 16:12:52 -07:00 • committed by GitHub
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@ -158,6 +158,6 @@ For example, functions like `insert`, `remove` and `move` from the `table` libra
## Improved garbage collector pacing
Luau uses an incremental garbage collector which does a little bit of work every so often, and at no point does it stop the world to go through the entire heap. The runtime will make sure that the collector runs interspersed with the program execution as the program allocates additional memory, which is known as "garbage collection assists", and can also run in response to explicit garbage collection invocation. In interactive environments such as video game engines it's possible, and even desireable, to request garbage collection every frame to make sure assists are minimized, since that allows scheduling the garbage collection to run concurrently with other engine processing that doesn't involve script execution.
Luau uses an incremental garbage collector which does a little bit of work every so often, and at no point does it stop the world to traverse the entire heap. The runtime will make sure that the collector runs interspersed with the program execution as the program allocates additional memory, which is known as "garbage collection assists", and can also run in response to explicit garbage collection invocation via `lua_gc`. In interactive environments such as video game engines it's possible, and even desireable, to request garbage collection every frame to make sure assists are minimized, since that allows scheduling the garbage collection to run concurrently with other engine processing that doesn't involve script execution.
Inspired by excellent work by Austin Clements on Go's garbage collector pacer, we've implemented a pacing algorithm that uses a proportional–integral–derivative controller to estimate internal garbage collector tunables to reach a target heap size, defined as a percentage of the live heap data (which is more intuitive and actionable than Lua 5.x "GC pause" setting). Luau runtime also estimates the allocation rate making it easy (when allocation rates do not vary much) to adjust the per-frame garbage collection requests to do most of the required GC work outside of script execution.
Inspired by excellent work by Austin Clements on Go's garbage collector pacer, we've implemented a pacing algorithm that uses a proportional–integral–derivative controller to estimate internal garbage collector tunables to reach a target heap size, defined as a percentage of the live heap data (which is more intuitive and actionable than Lua 5.x "GC pause" setting). Luau runtime also estimates the allocation rate making it easy (given uniform allocation rates) to adjust the per-frame garbage collection requests to do most of the required GC work outside of script execution.