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};