The malloc implementation you provided is based on the dlmalloc (Doug Lea's Malloc) algorithm. This is a general-purpose allocator that is widely used due to its combination of speed and efficient use of memory.
The main concepts behind dlmalloc are:
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Chunk: The basic unit of memory allocation. Each chunk contains a header with size and status information, and a payload where user data is stored.
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Bin: A collection of free chunks of similar sizes. There are small bins (for small chunks) and tree bins (for large chunks).
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Segment: A large chunk of memory obtained from the system. Segments are divided into chunks which are then allocated to the user or stored in bins.