1 清单 1. Linux 大页面应用示例 2  #include <fcntl.h>  3  #include <sys/mman.h>  4  #include <errno.h>  5  6  #define MAP_LENGTH      (10*1024*1024)  7  8  int main()  9  { 10     int fd; 11     void * addr; 12 13     /* create a file in hugetlb fs */ 14     fd = open("/mnt/huge/test", O_CREAT | O_RDWR); 15     if(fd < 0){ 16         perror("Err: "); 17         return -1; 18     }   19 20     /* map the file into address space of current application process */ 21     addr = mmap(0, MAP_LENGTH, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); 22     if(addr == MAP_FAILED){ 23         perror("Err: "); 24         close(fd); 25         unlink("/mnt/huge/test"); 26         return -1; 27     }   28 29     /* from now on, you can store application data on huage pages via addr */ 30 31     munmap(addr, MAP_LENGTH); 32     close(fd); 33     unlink("/mnt/huge/test"); 34     return 0; 35  }

 1 static int __init hugetlb_init(void) 2 { 3     /* Some platform decide whether they support huge pages at boot 4      * time. On these, such as powerpc, HPAGE_SHIFT is set to 0 when 5      * there is no such support 6      */ 7     if (HPAGE_SHIFT == 0) 8         return 0; 9 10     if (!size_to_hstate(default_hstate_size)) {11         default_hstate_size = HPAGE_SIZE;　　/*默认大小为2M*/12         if (!size_to_hstate(default_hstate_size))13 　　　　　　　/* 初始化hstates[MAX_NUMNODES]数组，数组中只有一个成员;14 　　　　　　　 * HUGETLB_PAGE_ORDER = 9,即，h->order = 9;15 　　　　　　　 */16 　　　　　　　hugetlb_add_hstate(HUGETLB_PAGE_ORDER);17     }18 　　 /*由于hstates[]只有一个成员，default_hstate_idx = 0*/19     default_hstate_idx = size_to_hstate(default_hstate_size) - hstates;20 　　 /*默认最大页数为0*/21     if (default_hstate_max_huge_pages)22         default_hstate.max_huge_pages = default_hstate_max_huge_pages;23 24 　　/*由于最大页数为0，没有为hstate[]分配任何页*/25 　　hugetlb_init_hstates();26 　　/*这个函数不知道干啥？？？*/27 　　gather_bootmem_prealloc();28 　　/*打印初始化后的相关信息*/29 　　report_hugepages();30 　　/*初始化/sys/kernel/mm/hugepages相关目录文件*/31 　　hugetlb_sysfs_init();32 　　/*初始化/sys/device/system/node/node*/hugepages相关目录文件*/33 　　hugetlb_register_all_nodes();34 　　return 0;35 }36 module_init(hugetlb_init);

1 static int __init hugetlb_default_setup(char *s)2 {3     default_hstate_size = memparse(s, &s);4     return 1;5 }6 __setup("default_hugepagesz=", hugetlb_default_setup);

 1 static int __init hugetlb_nrpages_setup(char *s) 2 { 3     unsigned long *mhp; 4     static unsigned long *last_mhp; 5     /* 6      * !max_hstate means we haven‘t parsed a hugepagesz= parameter yet, 7      * so this hugepages= parameter goes to the "default hstate". 8      */ 9     if (!max_hstate)10         mhp = &default_hstate_max_huge_pages;11     else12         mhp = &parsed_hstate->max_huge_pages;13     if (mhp == last_mhp) {14         printk(KERN_WARNING "hugepages= specified twice without "15             "interleaving hugepagesz=, ignoring\n");16         return 1;17     }18     if (sscanf(s, "%lu", mhp) <= 0)19         *mhp = 0;20     /*21      * Global state is always initialized later in hugetlb_init.22      * But we need to allocate >= MAX_ORDER hstates here early to still23      * use the bootmem allocator.24      */25 　　　/* parsed_hstate->order = 9, MAX_ORDER = 11, 不会调用hugetlb_hstate_alloc_pages();26 　　　 * 通过内核启动参数配置页面数，什么时候分配具体的内存页？？？27 　　　 */28     if (max_hstate && parsed_hstate->order >= MAX_ORDER)29         hugetlb_hstate_alloc_pages(parsed_hstate);30     last_mhp = mhp;31     return 1;32 }33 __setup("hugepages=", hugetlb_nrpages_setup);

1 int hugetlb_sysctl_handler(struct ctl_table *table, int write,2               void __user *buffer, size_t *length, loff_t *ppos)3 {4     return hugetlb_sysctl_handler_common(false, table, write,5                             buffer, length, ppos);6 }

 1 static int hugetlb_sysctl_handler_common(bool obey_mempolicy, 2              struct ctl_table *table, int write, 3              void __user *buffer, size_t *length, loff_t *ppos) 4 { 5     struct hstate *h = &default_hstate; 6     unsigned long tmp; 7     int ret; 8     tmp = h->max_huge_pages; 9     if (write && h->order >= MAX_ORDER)10         return -EINVAL;11     table->data = http://www.mamicode.com/&tmp;12     table->maxlen = sizeof(unsigned long);13 　　/*从用户空间将数值copy赋值给tabel->data，即tmp，并做相关检查*/14     ret = proc_doulongvec_minmax(table, write, buffer, length, ppos);15     if (ret)16         goto out;17     if (write) {        18 　　　　　　　　　 NODEMASK_ALLOC(nodemask_t, nodes_allowed, GFP_KERNEL | __GFP_NORETRY);19         if (!(obey_mempolicy &&20                    init_nodemask_of_mempolicy(nodes_allowed))) {21             NODEMASK_FREE(nodes_allowed);22             nodes_allowed = &node_states[N_HIGH_MEMORY];23         }24 　　　　　/*设置最大页数，并分配具体内存页*/25         h->max_huge_pages = set_max_huge_pages(h, tmp, nodes_allowed);26         if (nodes_allowed != &node_states[N_HIGH_MEMORY])27             NODEMASK_FREE(nodes_allowed);28     }29 out:30     return ret;31 }

 1 static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count, 2                         nodemask_t *nodes_allowed) 3 { 4     unsigned long min_count, ret; 5     if (h->order >= MAX_ORDER) 6         return h->max_huge_pages; 7     /* 8      * Increase the pool size 9      * First take pages out of surplus state.  Then make up the10      * remaining difference by allocating fresh huge pages.11      *12      * We might race with alloc_buddy_huge_page() here and be unable13      * to convert a surplus huge page to a normal huge page. That is14      * not critical, though, it just means the overall size of the15      * pool might be one hugepage larger than it needs to be, but16      * within all the constraints specified by the sysctls.17      */18     spin_lock(&hugetlb_lock);19     while (h->surplus_huge_pages && count > persistent_huge_pages(h)) {20         if (!adjust_pool_surplus(h, nodes_allowed, -1))21             break;22     }23     while (count > persistent_huge_pages(h)) {24         /*25          * If this allocation races such that we no longer need the26          * page, free_huge_page will handle it by freeing the page27          * and reducing the surplus.28          */29         spin_unlock(&hugetlb_lock);30 　　　　　/*分配内存页*/31         ret = alloc_fresh_huge_page(h, nodes_allowed);32         spin_lock(&hugetlb_lock);33         if (!ret)34             goto out;35         /* Bail for signals. Probably ctrl-c from user */36         if (signal_pending(current))37             goto out;38     }39     /*40      * Decrease the pool size41      * First return free pages to the buddy allocator (being careful42      * to keep enough around to satisfy reservations).  Then place43      * pages into surplus state as needed so the pool will shrink44      * to the desired size as pages become free.45      *46      * By placing pages into the surplus state independent of the47      * overcommit value, we are allowing the surplus pool size to48      * exceed overcommit. There are few sane options here. Since49      * alloc_buddy_huge_page() is checking the global counter,50      * though, we‘ll note that we‘re not allowed to exceed surplus51      * and won‘t grow the pool anywhere else. Not until one of the52      * sysctls are changed, or the surplus pages go out of use.53      */54     min_count = h->resv_huge_pages + h->nr_huge_pages - h->free_huge_pages;55     min_count = max(count, min_count);56     try_to_free_low(h, min_count, nodes_allowed);57     while (min_count < persistent_huge_pages(h)) {58         if (!free_pool_huge_page(h, nodes_allowed, 0))59             break;60     }61     while (count < persistent_huge_pages(h)) {62         if (!adjust_pool_surplus(h, nodes_allowed, 1))63             break;64     }65 out:66     ret = persistent_huge_pages(h);67     spin_unlock(&hugetlb_lock);68     return ret;69 }

 1 static int alloc_fresh_huge_page(struct hstate *h, nodemask_t *nodes_allowed) 2 { 3     struct page *page; 4     int start_nid; 5     int next_nid; 6     int ret = 0; 7     start_nid = hstate_next_node_to_alloc(h, nodes_allowed); 8     next_nid = start_nid; 9     do {10 　　　　　/* 从内存Node的zonelist上分配2^h->order个4K的内存页，返回第一个page的地址；11 　　　　　 * 如果分配不成功，从下一个内存Node上尝试；12 　　　　　 */13         page = alloc_fresh_huge_page_node(h, next_nid);14         if (page) {15             ret = 1;16             break;17         }18         next_nid = hstate_next_node_to_alloc(h, nodes_allowed);19     } while (next_nid != start_nid);20     if (ret)21         count_vm_event(HTLB_BUDDY_PGALLOC);22     else23         count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);24     return ret;25 }

 1 static struct page *alloc_fresh_huge_page_node(struct hstate *h, int nid) 2 { 3     struct page *page; 4     if (h->order >= MAX_ORDER) 5         return NULL; 6     /*__GFP_COMP标志：分配2^h->order个连续的4K大小的page，返回第一个Page的地址，并设置PG_compound标记*/ 7 　　 page = alloc_pages_exact_node(nid, 8 　　 htlb_alloc_mask|__GFP_COMP|__GFP_THISNODE| 9                         __GFP_REPEAT|__GFP_NOWARN,10 　　 huge_page_order(h));11     if (page) {12         if (arch_prepare_hugepage(page)) {13             __free_pages(page, huge_page_order(h));14             return NULL;15         }16 　　　　　/* 1、将已分配的2^h->order个数的page中的第二个page的lru.next执行函数free_huge_page()；17 　　　　　 * 2、在put_page()函数中，最后调用free_huge_page()-->enqueue_huge_page()，将page加入到h->hugepages_freelists[nid]链表；18 　　　　　 */19         prep_new_huge_page(h, page, nid);20     }21     return page;22 }

 1 static int __init init_hugetlbfs_fs(void) 2 { 3     int error; 4     struct vfsmount *vfsmount; 5  6     /*初始化hugetlbfs回写数据结构*/ 7     error = bdi_init(&hugetlbfs_backing_dev_info); 8     if (error) 9         return error;10 11     error = -ENOMEM;12     /*创建slab缓存hugetlbfs_inode_cachep，后续hugetlbfs的inode从这里面分配*/13     hugetlbfs_inode_cachep = kmem_cache_create("hugetlbfs_inode_cache",14                     sizeof(struct hugetlbfs_inode_info),15                     0, 0, init_once);16     if (hugetlbfs_inode_cachep == NULL)17         goto out2;18 19     /*将hugetlbfs_fs_type加入到全局file_systems链表中*/20     error = register_filesystem(&hugetlbfs_fs_type);21     if (error)22         goto out;23 24     /* 创建hugetlbfs的super_block、entry、inode，并建立它们之间的相互映射，25 　　　* 以及它们与hugetlbfs_fs_type、default_hstate、hugetlbfs_inode_cachep之间的映射关系26 　　　*/27     vfsmount = kern_mount(&hugetlbfs_fs_type);28 29     if (!IS_ERR(vfsmount)) {30         hugetlbfs_vfsmount = vfsmount;31         return 0;32     }33 34     error = PTR_ERR(vfsmount);35 36  out:37     kmem_cache_destroy(hugetlbfs_inode_cachep);38  out2:39     bdi_destroy(&hugetlbfs_backing_dev_info);40     return error;41 }42