Linux kernel 什么；删除“；是否在/proc/$pid/maps中表示？

我下载了libhugetlbfs.so，并有一个简单的测试源：

int glbarr[1024*1024]={0} ;
int main()
{
    char * ptr ;
    ptr = (char *) malloc( 1024 * 1024 * 1 ) ;
    printf(" press any key to go on \n");
    getchar() ;
    for(int idx=0;idx<100;idx++){
        char strtmp[64] = {0} ;
        sprintf(strtmp,"%020d",idx) ;
        strcpy( ptr+1024*idx , strtmp ) ;
    } //for 
    for(int idx=0;idx<100;idx++){
        glbarr[idx] = idx ;
    }
    printf(" press any key to go on \n");
    getchar() ;
} // main

最后，执行test_malloc.exe：

 INFO: Found pagesize 2048 kB
 INFO: Detected page sizes:
 INFO:    Size: 2048 kB (default)  Mount: /mnt/SharedMem_2M
 INFO: Parsed kernel version: [3] . [10] . [0] 
 INFO: Feature private_reservations is present in this kernel
 INFO: Feature noreserve_safe is present in this kernel
 INFO: Feature map_hugetlb is present in this kernel
 INFO: Kernel has MAP_PRIVATE reservations.  Disabling heap prefaulting.
 INFO: Kernel supports MAP_HUGETLB
 INFO: HUGETLB_SHARE=0, sharing disabled
 INFO: HUGETLB_NO_RESERVE=no, reservations enabled
 INFO: Segment 0 (phdr 2): 0x400000-0x400a04  (filesz=0xa04) (prot = 0x5)
 INFO: Segment 1 (phdr 3): 0x600de0-0xa01080  (filesz=0x274) (prot = 0x3)
 DEBUG: symbol to copy at 0x601060: stdin
 DEBUG: Total memsz = 0x400ca4, memsz of largest segment = 0x4002a0
 INFO: libhugetlbfs version: 2.20
 INFO: Mapped hugeseg at 0x2aaaaac00000. Copying 0xa04 bytes and 0 extra bytes from 0x400000...done
 INFO: Prepare succeeded
 INFO: Mapped hugeseg at 0x2aaaaac00000. Copying 0x274 bytes and 0x14 extra bytes from 0x600de0...done
 INFO: Prepare succeeded
 INFO: setup_morecore(): heapaddr = 0x1c00000
 INFO: hugetlbfs_morecore(2101248) = ...
 INFO: heapbase = 0x1c00000, heaptop = 0x1c00000, mapsize = 0, delta=2101248
 INFO: Attempting to map 4194304 bytes
 INFO: ... = 0x1c00000
 INFO: hugetlbfs_morecore(0) = ...
 INFO: heapbase = 0x1c00000, heaptop = 0x1e01000, mapsize = 400000, delta=-2093056
 INFO: ... = 0x1e01000

和/proc/

pidof test_malloc.exe

/maps：

00400000-00600000 r-xp 00000000 00:2b 6019488                            /mnt/SharedMem_2M/libhugetlbfs.tmp.uI55WD (deleted)
00600000-00c00000 rw-p 00000000 00:2b 6123885                            /mnt/SharedMem_2M/libhugetlbfs.tmp.VUALYM (deleted)
01c00000-02000000 rw-p 00000000 00:0d 6123886                            /anon_hugepage (deleted)

numastat-m展示了hugepage在800万年内的实际使用情况， 让我烦恼的是“删除”在地图输出中意味着什么？！ 在/mnt/SharedMem_2M或/anon_hugepage中

编辑：

以及调试信息：

INFO: Found pagesize 2048 kB
INFO: Detected page sizes:
INFO:    Size: 2048 kB (default)  Mount: /mnt/SharedMem_2M
INFO: Parsed kernel version: [3] . [10] . [0] 
INFO: Feature private_reservations is present in this kernel
INFO: Feature noreserve_safe is present in this kernel
INFO: Feature map_hugetlb is present in this kernel
INFO: Kernel has MAP_PRIVATE reservations.  Disabling heap prefaulting.
INFO: Kernel supports MAP_HUGETLB
INFO: HUGETLB_SHARE=0, sharing disabled
INFO: HUGETLB_NO_RESERVE=no, reservations enabled
INFO: Segment 0 (phdr 3): 0x600de0-0xa01080  (filesz=0x274) (prot = 0x3)
DEBUG: symbol to copy at 0x601060: stdin
DEBUG: Total memsz = 0x4002a0, memsz of largest segment = 0x4002a0
INFO: libhugetlbfs version: 2.20
INFO: Mapped hugeseg at 0x2aaaaac00000. Copying 0x274 bytes and 0x14 extra bytes from 0x600de0...done
INFO: Prepare succeeded
INFO: setup_morecore(): heapaddr = 0x2200000
INFO: hugetlbfs_morecore(2101248) = ...
INFO: heapbase = 0x2200000, heaptop = 0x2200000, mapsize = 0, delta=2101248
INFO: Attempting to map 4194304 bytes
INFO: ... = 0x2200000
INFO: hugetlbfs_morecore(0) = ...
INFO: heapbase = 0x2200000, heaptop = 0x2401000, mapsize = 400000, delta=-2093056
INFO: ... = 0x2401000

以及地图：

00400000 default file=/home/marschen/test/posix-memalign/test_malloc.exe mapped=1 N0=1 kernelpagesize_kB=4
00600000 default file=/mnt/SharedMem_2M/libhugetlbfs.tmp.85Y41e\040(deleted) huge anon=1 dirty=1 N0=1 kernelpagesize_kB=2048
02200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N0=1 kernelpagesize_kB=2048

当libhugetlbfs使用hugetlb-fs伪文件系统（

grep-hugetlbfs/proc/filesystems

）来获取支持hugetlb页面的mmap时，临时文件删除（取消链接）对于libhugetlbfs来说是正常的

例如，libhugetlbfs/hugeutils.c有

hugetlbfs\u unlinked\u fd

函数

在mkstemp函数中随机生成临时文件名；它还创建并打开文件。然后该文件与文件系统解除链接（）（文件名在目录中标记为已删除，仍然有inode和文件数据，但其他程序无法按名称访问该文件）

当打开未链接的

fd

时，它可用于处理hugetlb mmap和存储数据。只有当此fd关闭时，文件数据才会被fs实际删除

通常使用mktemp文件的早期取消链接：

libhugetlbfs项目的HOWTO中还列出了一些有用的信息

---

“已删除”是指名为MMA的文件，然后从fs的可见部分删除。它仍然由fs处理（使用hugepages for MMAP），但现在无法与其他进程共享（无法打开文件）。你的问题是什么？你能在没有

--text

选项的情况下发布相同的结果吗？libhugetlbfs可能会在执行之前将文本部分复制到一些新的大型映射中。@osgx，谢谢，我的问题是为什么要在映射中（删除），如果这意味着我做了一些工作？！不，“已删除”并不意味着任何错误，它只是libhugetlbfs内部的工作方式（在某些情况下）它在专门装载的伪文件系统上创建文件，mmaps这个文件并取消链接（从fs中删除文件名）。进程运行时，文件数据仍由hugetlbfs处理。您的

grep-hugetlbfs/proc/filesystems

是什么？@osgx，感谢nodev-hugetlbfs为grep-hugetlbfs/proc/filesystems提供的帮助

00400000 default file=/home/marschen/test/posix-memalign/test_malloc.exe mapped=1 N0=1 kernelpagesize_kB=4
00600000 default file=/mnt/SharedMem_2M/libhugetlbfs.tmp.85Y41e\040(deleted) huge anon=1 dirty=1 N0=1 kernelpagesize_kB=2048
02200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N0=1 kernelpagesize_kB=2048

int hugetlbfs_unlinked_fd_for_size(long page_size)
{
    const char *path;
    char name[PATH_MAX+1];
    int fd;

    path = hugetlbfs_find_path_for_size(page_size);
    ..
    name[sizeof(name)-1] = '\0';

    strcpy(name, path);
    strncat(name, "/libhugetlbfs.tmp.XXXXXX", sizeof(name)-1);
    /* FIXME: deal with overflows */

    fd = mkstemp64(name);
    ....

    unlink(name);

    return fd;
}