【Linux 内核 内存管理】Linux 内核堆内存管理 ① ( 堆内存管理 | 内存描述符 mm_struct 结构体 | mm_struct 结构体中的 start_brk、brk 成员 )

struct mm_struct {
	struct {
		struct vm_area_struct *mmap;		/* list of VMAs */
		struct rb_root mm_rb;
		u64 vmacache_seqnum;                   /* per-thread vmacache */

		// ...

		unsigned long hiwater_rss; /* High-watermark of RSS usage */
		unsigned long hiwater_vm;  /* High-water virtual memory usage */

		unsigned long total_vm;	   /* Total pages mapped */
		unsigned long locked_vm;   /* Pages that have PG_mlocked set */
		atomic64_t    pinned_vm;   /* Refcount permanently increased */
		unsigned long data_vm;	   /* VM_WRITE & ~VM_SHARED & ~VM_STACK */
		unsigned long exec_vm;	   /* VM_EXEC & ~VM_WRITE & ~VM_STACK */
		unsigned long stack_vm;	   /* VM_STACK */
		unsigned long def_flags;

		spinlock_t arg_lock; /* protect the below fields */
		unsigned long start_code, end_code, start_data, end_data;
		unsigned long start_brk, brk, start_stack;
		unsigned long arg_start, arg_end, env_start, env_end;

		unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */
		// ...
	} __randomize_layout;

	/*
	 * The mm_cpumask needs to be at the end of mm_struct, because it
	 * is dynamically sized based on nr_cpu_ids.
	 */
	unsigned long cpu_bitmap[];
};

		unsigned long start_brk, brk, start_stack;