本文出自: http://blog.csdn.net/hongchangfirst

        上次讲了Linux进程描述符，这次我们在讲讲内存描述符，Linux的内存描述符也用一个结构体来表示，具体是mm_struct结构体，在linux/mm_types.h里定义。Linux操作系统就是用这个结构体实现内存的管理，我们先看一下具体的字段情况。

 

struct mm_struct {

//拥有该结构体的进程的虚拟地址空间的大小
 unsigned long task_size;  

/* if non-zero, the largest hole below free_area_cache */
 unsigned long cached_hole_size; 

/* first hole of size cached_hole_size or larger */
  unsigned long free_area_cache; 

//在用户空间下有多少用户使用该内存

 atomic_t mm_users;   /* How many users with user space? */


//该结构体的引用计数值
 atomic_t mm_count;  
 

/*又出现了list_head,详情请参考，简单来讲，list_head和list_for_each、list_entry共同实现了其“包含体”的链表。*/

 struct list_head mmlist;  


/*以下是关于代码段、数据段，栈、环境变量、参数的起始地址或结束地址等*/
 unsigned long total_vm, locked_vm, shared_vm, exec_vm;
 unsigned long stack_vm, reserved_vm, def_flags, nr_ptes;
 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;

  /*
  * Last value of global fault stamp as seen by this process.
  * In other words, this value gives an indication of how long
  * it has been since this task got the token.
  * Look at mm/thrash.c
  */
 unsigned int faultstamp;
 unsigned int token_priority;
 unsigned int last_interval;

};

       该结构体可以通过进程描述符来得到，比如current是当前进程的描述符，则current->mm是指向内存的指针。mm是指向struct mm_struct的指针。若还想对Linux的进程描述符有一定了解，可以参考task_struct。