The semantics of v8::ResourceConstraints?

问题

The v8::ResourceConstraints class is defined as follows:

class V8EXPORT ResourceConstraints {
 public:
  ResourceConstraints();
  int max_young_space_size() const { return max_young_space_size_; }
  void set_max_young_space_size(int value) { max_young_space_size_ = value; }
  int max_old_space_size() const { return max_old_space_size_; }
  void set_max_old_space_size(int value) { max_old_space_size_ = value; }
  int max_executable_size() { return max_executable_size_; }
  void set_max_executable_size(int value) { max_executable_size_ = value; }
  uint32_t* stack_limit() const { return stack_limit_; }
  // Sets an address beyond which the VM's stack may not grow.
  void set_stack_limit(uint32_t* value) { stack_limit_ = value; }
 private:
  int max_young_space_size_;
  int max_old_space_size_;
  int max_executable_size_;
  uint32_t* stack_limit_;
};

Can someone tell me what young_space_size, old_space_size, and max_executable_size are? What are their units, how are they related, etc.? There doesn't seem to be much documentation.

Also, how does one use the stack_limit property? For example, if I want my V8 isolate to use no more than 1MB of stack space, how would I calculate a pointer value for stack_limit?

回答1:

v8/test/cctest/test-api.cc uses this function to calculate the limit:

// Uses the address of a local variable to determine the stack top now.
// Given a size, returns an address that is that far from the current
// top of stack.
static uint32_t* ComputeStackLimit(uint32_t size) {
  uint32_t* answer = &size - (size / sizeof(size));
  // If the size is very large and the stack is very near the bottom of
  // memory then the calculation above may wrap around and give an address
  // that is above the (downwards-growing) stack.  In that case we return
  // a very low address.
  if (answer > &size) return reinterpret_cast<uint32_t*>(sizeof(size));
  return answer;
}

来源：https://stackoverflow.com/questions/15583446/the-semantics-of-v8resourceconstraints

标签

embedded-v8