Stuff Goes Bad:Erlang In Anger


Erlang’s binaries are of two main types: ProcBins and Refc binaries 8. Binaries up to 64 bytes are allocated directly on the process’s heap, and their entire life cycle is spent in there. Binaries bigger than that get allocated in a global heap for binaries only, and each process to use one holds a local reference to it in its local heap. These binaries are referencecounted, and the deallocation will occur only once all references are garbage-collected from all processes that pointed to a specific binary.
 In 99% of the cases, this mechanism works entirely fine. In some cases, however, the process will either:
 1. do too little work to warrant allocations and garbage collection;
 2. eventually grow a large stack or heap with various data structures, collect them, then get to work with a lot of refc binaries. Filling the heap again with binaries (even though a virtual heap is used to account for the refc binaries’ real size) may take a lot of time, giving long delays between garbage collections.

 Erlang的binaries有两种主要的类型:ProBins和Refc binaries8。Binaries大于64 字节的都会被直接分配到进程的堆中,他们的一生都将呆在那里。比那更大的binaries会被分配到专用于存binaries的全局堆里面,每个使用它的进程都有一个对应它的本地引用存在自己的本地堆中。这些binaries是引用计数的,会在所有关于它的本地引用都被垃圾回收后真正释放掉。

 1. 对于保证分配和垃圾回收,做的工作太少。
 2. 最终生成了一个有各种数据结构的大堆栈,并把他们汇聚到一起,然后与大量的refc binaries混合在一起工作。再次用binaries填充满堆(即使只是一个用于映射refc binaries的虚拟堆),这可能会消耗大量时间,造成垃圾回收被延迟。