glibc malloc

Based on ptmalloc .

Heap Creation

Checking brk or malloc

1. If parent thread, and memory wanted exceeds C Macro DEFAULT_MMAP_THRESHOLD, then allocate with mmap()
2. Else, we setup with brk()

Setup with brk()

• End_data : pointer that sets end of data segment
• start_brk : pointer that denotes beginning of heap
• Brk / program break : pointer that denotes end of heap segment
• brk() used to initialize end_data to the value specificied by addr
• start_brk set to next available segment after data segment
• brk = start_brk
• To expand/shrink dimensions of heap, sbrk() is used

Setup with mmap()

we mmap() things at the Memory Map Segment