It may still cheat in the sense that it may recycle existing blocks of memories or otherwise delay allocation. Then the operating system actually needs to allocate and initialize memory 2. You can achieve the desired result in C++ by adding parentheses after the call to the new operator: char *buf = new char ( ) If you actually want to measure the memory allocation in C++, then you need to ask the system to give you s bytes of allocated and initialized memory. The great thing with a virtual allocation is that if you never access the memory, you may never pay a price for it. ![]() Thus the cost of memory allocation can be hidden. As you access the memory buffer, the system may then decide to allocate the memory pages (often in blocks of 4096 bytes). But that is because we are cheating: the call to the new operation “virtually” allocates the memory, but you may not yet have actual memory that you can use. If you benchmark this line of code, you might find that it almost entirely free on a per-byte basis for large values of s. In C++, the most basic memory allocation code is just a call to the new operator: char *buf = new char Īccording to a textbook interpretation, we just allocated s bytes 1. jerch on Hotspot performance engineering fails.Daniel Lemire on Hotspot performance engineering fails. ![]()
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