Linux内存描述符mm_struct实例详解

struct mm_struct {
  struct vm_area_struct * mmap;  //指向虚拟区间(VMA)的链表
  struct rb_root mm_rb;      //指向线性区对象红黑树的根
  struct vm_area_struct * mmap_cache;   //指向最近找到的虚拟区间
  unsigned long(*get_unmapped_area) (struct file *filp,
  unsigned long addr, unsigned long len,
  unsigned long pgoff, unsigned long flags);//在进程地址空间中搜索有效线性地址区
  unsigned long(*get_unmapped_exec_area) (struct file *filp,
    unsigned long addr, unsigned long len,
    unsigned long pgoff, unsigned long flags);
  void(*unmap_area) (struct mm_struct *mm, unsigned long addr);//释放线性地址区间时调用的方法
  unsigned long mmap_base;        /* base of mmap area */
  unsigned long task_size;        /* size of task vm space */
  unsigned long cached_hole_size;
  unsigned long free_area_cache;     //内核从这个地址开始搜索进程地址空间中线性地址的空闲区域
  pgd_t * pgd;              //指向页全局目录
  atomic_t mm_users;           //次使用计数器，使用这块空间的个数  
  atomic_t mm_count;           //主使用计数器
  int map_count;             //线性的个数
  struct rw_semaphore mmap_sem;      //线性区的读/写信号量
  spinlock_t page_table_lock;       //线性区的自旋锁和页表的自旋锁
  struct list_head mmlist;       //指向内存描述符链表中的相邻元素
  /* Special counters, in some configurations protected by the
  * page_table_lock, in other configurations by being atomic.
  */
  mm_counter_t _file_rss; //mm_counter_t代表的类型实际是typedef atomic_long_t
  mm_counter_t _anon_rss; 
  mm_counter_t _swap_usage;
  unsigned long hiwater_rss;  //进程所拥有的最大页框数
  unsigned long hiwater_vm;   //进程线性区中最大页数
  unsigned long total_vm, locked_vm, shared_vm, exec_vm;
  //total_vm 进程地址空间的大小(页数）
  //locked_vm 锁住而不能换出的页的个数
  //shared_vm 共享文件内存映射中的页数
  unsigned long stack_vm, reserved_vm, def_flags, nr_ptes;
  //stack_vm 用户堆栈中的页数
  //reserved_vm 在保留区中的页数或者在特殊线性区中的页数
  //def_flags 线性区默认的访问标志
  //nr_ptes 进程的页表数
  unsigned long start_code, end_code, start_data, end_data;
  //start_code 可执行代码的起始地址
  //end_code 可执行代码的最后地址
  //start_data已初始化数据的起始地址
  // end_data已初始化数据的最后地址
  unsigned long start_brk, brk, start_stack;
  //start_stack堆的起始位置
  //brk堆的当前的最后地址
  //用户堆栈的起始地址
  unsigned long arg_start, arg_end, env_start, env_end;
  //arg_start 命令行参数的起始地址
  //arg_end命令行参数的起始地址
  //env_start环境变量的起始地址
  //env_end环境变量的最后地址
  unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */
  struct linux_binfmt *binfmt;
  cpumask_t cpu_vm_mask; //用于惰性TLB交换的位掩码
  /* Architecture-specific MM context */
  mm_context_t context; //指向有关特定结构体系信息的表
  unsigned int faultstamp;
  unsigned int token_priority;
  unsigned int last_interval;
  unsigned long flags; /* Must use atomic bitops to access the bits */
  struct core_state *core_state; /* coredumping support */
#ifdef CONFIG_AIO
  spinlock_t       ioctx_lock; //用于保护异步I/O上下文链表的锁
  struct hlist_head    ioctx_list;//异步I/O上下文
#endif
#ifdef CONFIG_MM_OWNER
  struct task_struct *owner;
#endif
#ifdef CONFIG_PROC_FS
  unsigned long num_exe_file_vmas;
#endif
#ifdef CONFIG_MMU_NOTIFIER
  struct mmu_notifier_mm *mmu_notifier_mm;
#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
  pgtable_t pmd_huge_pte; /* protected by page_table_lock */
#endif
#ifdef __GENKSYMS__
  unsigned long rh_reserved[2];
#else
  //有多少任务分享这个mm OOM_DISABLE
  union {
    unsigned long rh_reserved_aux;
    atomic_t oom_disable_count;
  };
  /* base of lib map area (ASCII armour) */
  unsigned long shlib_base;
#endif
};