1 struct mm_struct {
  2     struct vm_area_struct * mmap;    //指向虚拟区间(VMA)的链表
  3     struct rb_root mm_rb;            //指向线性区对象红黑树的根
  4     struct vm_area_struct * mmap_cache;     //指向最近找到的虚拟区间
  5     unsigned long(*get_unmapped_area) (struct file *filp,
  6     unsigned long addr, unsigned long len,
  7     unsigned long pgoff, unsigned long flags);//在进程地址空间中搜索有效线性地址区
  8     unsigned long(*get_unmapped_exec_area) (struct file *filp,
  9         unsigned long addr, unsigned long len,
 10         unsigned long pgoff, unsigned long flags);
 11     void(*unmap_area) (struct mm_struct *mm, unsigned long addr);//释放线性地址区间时调用的方法
 12     unsigned long mmap_base;                /* base of mmap area */
 13     unsigned long task_size;                /* size of task vm space */
 14
 15     unsigned long cached_hole_size;
 16     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
 17     pgd_t * pgd;                            //指向页全局目录
 18     atomic_t mm_users;                      //次使用计数器，使用这块空间的个数
 19     atomic_t mm_count;                      //主使用计数器
 20     int map_count;                          //线性的个数
 21     struct rw_semaphore mmap_sem;           //线性区的读/写信号量
 22     spinlock_t page_table_lock;             //线性区的自旋锁和页表的自旋锁
 23
 24     struct list_head mmlist;              //指向内存描述符链表中的相邻元素
 25
 26     /* Special counters, in some configurations protected by the
 27     * page_table_lock, in other configurations by being atomic.
 28     */
 29     mm_counter_t _file_rss; //mm_counter_t代表的类型实际是typedef atomic_long_t
 30     mm_counter_t _anon_rss;
 31     mm_counter_t _swap_usage;
 32
 33     unsigned long hiwater_rss;    //进程所拥有的最大页框数
 34     unsigned long hiwater_vm;     //进程线性区中最大页数
 35
 36     unsigned long total_vm, locked_vm, shared_vm, exec_vm;
 37     //total_vm 进程地址空间的大小(页数）
 38     //locked_vm 锁住而不能换出的页的个数
 39     //shared_vm 共享文件内存映射中的页数
 40
 41     unsigned long stack_vm, reserved_vm, def_flags, nr_ptes;
 42     //stack_vm 用户堆栈中的页数
 43     //reserved_vm 在保留区中的页数或者在特殊线性区中的页数
 44     //def_flags 线性区默认的访问标志
 45     //nr_ptes 进程的页表数
 46
 47     unsigned long start_code, end_code, start_data, end_data;
 48     //start_code 可执行代码的起始地址
 49     //end_code 可执行代码的最后地址
 50     //start_data已初始化数据的起始地址
 51     // end_data已初始化数据的最后地址
 52
 53     unsigned long start_brk, brk, start_stack;
 54     //start_stack堆的起始位置
 55     //brk堆的当前的最后地址
 56     //用户堆栈的起始地址
 57
 58     unsigned long arg_start, arg_end, env_start, env_end;
 59     //arg_start 命令行参数的起始地址
 60     //arg_end命令行参数的起始地址
 61     //env_start环境变量的起始地址
 62     //env_end环境变量的最后地址
 63
 64     unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */
 65
 66     struct linux_binfmt *binfmt;
 67
 68     cpumask_t cpu_vm_mask; //用于惰性TLB交换的位掩码
 69     /* Architecture-specific MM context */
 70     mm_context_t context; //指向有关特定结构体系信息的表
 71
 72
 73     unsigned int faultstamp;
 74     unsigned int token_priority;
 75     unsigned int last_interval;
 76
 77     unsigned long flags; /* Must use atomic bitops to access the bits */
 78
 79     struct core_state *core_state; /* coredumping support */
 80 #ifdef CONFIG_AIO
 81     spinlock_t              ioctx_lock;  //用于保护异步I/O上下文链表的锁
 82     struct hlist_head       ioctx_list;//异步I/O上下文
 83 #endif
 84 #ifdef CONFIG_MM_OWNER
 85     struct task_struct *owner;
 86 #endif
 87
 88 #ifdef CONFIG_PROC_FS
 89     unsigned long num_exe_file_vmas;
 90 #endif
 91 #ifdef CONFIG_MMU_NOTIFIER
 92     struct mmu_notifier_mm *mmu_notifier_mm;
 93 #endif
 94 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 95     pgtable_t pmd_huge_pte; /* protected by page_table_lock */
 96 #endif
 97 #ifdef __GENKSYMS__
 98     unsigned long rh_reserved[2];
 99 #else
100     //有多少任务分享这个mm OOM_DISABLE
101     union {
102         unsigned long rh_reserved_aux;
103         atomic_t oom_disable_count;
104     };
105
106     /* base of lib map area (ASCII armour) */
107     unsigned long shlib_base;
108 #endif
109 };