内存mmap实现原理

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1、内存mmap实现原理内存mmap实现原理谨以此文纪念过往的岁月。结构体列表1.structrb_node_s2structpage3.structvm_area_struct4.structmm_struct函数列表do_mmapdo_mmap2红黑树结构    Linux内核从2.4.10开始，对虚拟区的组织不再采用AVL树，而是采用红黑树，这也是出于效率的考虑，虽然AVL树和红黑树很类似，但在插入和删除节点方面，采用红黑树的性能更好一些，下面对红黑树给予简单介绍。  一颗红黑树是具有以下特点的二叉树：（1）  每

2、个节点着有颜色，或者为红，或者为黑（2）  根节点为黑色（3）  如果一个节点为红色，那么它的子节点必须为黑色（4）  从一个节点到叶子节点上的所有路径都包含有相同的黑色节点数  红黑树的结构在include/linux/rbtree.h中定义如下：typedefstructrb_node_s{      structrb_node_s*rb_parent;      intrb_color;#defineRB_RED      0#defineRB_BLACK      1      structrb_node_s

3、*rb_right;      structrb_node_s*rb_left;}rb_node_t;O(∩_∩)O~structpage{      unsignedlongflags;        /*Atomicflags,somepossibly                                *updatedasynchronously*/      atomic_t_count;      /*Usagecount,seebelow.*/      union{            at

4、omic_t_mapcount;  /*Countofptesmappedinmms,                                *toshowwhenpageismapped                                *&limitreversemapsearches.                                */            struct{          /*SLUB*/                  u16inuse;       

5、           u16objects;            };      };      union{        struct{            unsignedlongprivate;            /*Mapping-privateopaquedata:                                      *usuallyusedforbuffer_heads                                      *ifPagePrivates

6、et;usedfor                                      *swp_entry_tifPageSwapCache;                                      *indicatesorderinthebuddy                                      *systemifPG_buddyisset.                                      */            structadd

7、ress_space*mapping;/*Iflowbitclear,pointsto                                      *inodeaddress_space,orNULL.                                      *Ifpagemappedasanonymous                                      *memory,lowbitisset,and                              

8、        *itpointstoanon_vmaobject:                                      *seePAGE_MAPPING_ANONbelow.                                      */        };#ifUSE_SPLIT_PTLOCKS