如何在 OSX 上创建没有备份文件的内存映射文件？
我想使用一个使用文件描述符作为访问其数据的基本手段的库。出于性能原因，我不想在使用该库的功能之前每次都将文件提交到磁盘。
我想动态创建（大型）数据 blob，并调用库将它们发送到服务器。按照目前的情况，我必须将文件写入磁盘，打开它，将 FD 传递到库，等待它完成，然后删除磁盘上的文件。由于我可以根据需要重新创建 blob（而且它们不会太大而导致过多的虚拟内存分页），因此将它们保存到磁盘不会给我带来任何好处，而且会带来很大的性能损失。
是否可以将 FD 分配给仅作为内存映射实体驻留的数据块？
I want to use a library that uses file descriptors as the basic means to access its data. For performance reasons, I don't want to have to commit files to the disk each before I use this library's functions.
I want to create (large) data blobs on the fly, and call into the library to send them to a server. As it stands, I have to write the file to disk, open it, pass the FD to the library, wait for it to finish, then delete the file on disk. Since I can re-create the blobs on demand (and they're not so large that they cause excessive virtual memory paging), saving them to disk buys me nothing, and incurs a large performance penalty.
Is it possible to assign a FD to a block of data that resides only as a memory-mapped entity?
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您可以安装内存支持的文件系统：http://lists.apple.com/archives/darwin-kernel/2004/Sep/msg00004.html
使用此机制会增加系统的内存压力，如果内存压力过大，可能会被换出页面足够棒了。如果用户希望其他应用程序优先选择内存，则将其作为配置选项可能是值得的。
另一种选择是使用POSIX共享内存段：http:// （我自己没有使用过 POSIX 共享内存段；如果我理解正确的话，它们就是为了解决这个问题而设计的。）
/opengroup.org/onlinepubs/007908799/xsh/shm_open.html shm_open()函数创建一个内存对象并返回一个文件描述符。然后，您可以
mmap(2)该文件描述符，完成您的工作，并将文件描述符传递给库。完成后，不要忘记
shm_unlink对象；当最后一个进程退出时，POSIX 共享内存段、消息队列和信号量数组不会自动消失。You could mount a memory-backed filesystem: http://lists.apple.com/archives/darwin-kernel/2004/Sep/msg00004.html
Using this mechanism will increase memory pressure on the system, and will probably be paged out if memory pressure is great enough. It might be worthwhile to make it a configuration option, in case the user would rather some other application have first-choice of the memory.
Another option is to use POSIX shared memory segments: http://opengroup.org/onlinepubs/007908799/xsh/shm_open.html (I haven't used POSIX shared memory segments myself; if I understand them correctly, they were designed to solve exactly this problem.)
The
shm_open()function creates a memory object and returns a file descriptor. You could thenmmap(2)that file descriptor, do your work, and pass the file descriptor to the library.Don't forget to
shm_unlinkthe object when you're done; POSIX shared memory segments, message queues, and semaphore arrays don't automatically go away when the last process exits.