[Python-Dev] Add sendfile() to core?

2002年3月20日 14:53:58 -0500

The Medusa distribution contains a small module that wraps the
sendfile() system call, available at least on Unix and FreeBSD. 
The man page explains what sendfile() does:
 ssize_t sendfile(int out_fd, int in_fd, off_t *offset,
 size_t count)
 This call copies data between one file descriptor and
 another. Either or both of these file descriptors may
 refer to a socket (but see below). in_fd should be a file
 descriptor opened for reading and out_fd should be a
 descriptor opened for writing. offset is a pointer to a
 variable holding the input file pointer position from
 which sendfile() will start reading data. When sendfile()
 returns, this variable will be set to the offset of the
 byte following the last byte that was read. count is the
 number of bytes to copy between file descriptors.
 Because this copying is done within the kernel, sendfile()
 does not need to spend time transferring data to and from
 user space.
sendfile() is used when writing really high-performance Web servers,
in order to save an unnecessary memory-to-memory copy. Question:
should I make up a patch to add a sendfile() wrapper to Python?
(Personally I think we can live without it. If you're writing servers
in Python, an interpreted language where creating an integer can end
up calling malloc(), then worrying about the cost of memory-to-memory
copying seems misplaced. Another strike against it is that it isn't
portable; other Unixes have similar but different calls with different
names.)
--amk (www.amk.ca)
 "Aww, c'mon! Where's your sense of fun?"
 "I'm the standard model, Zachary. 'Fun' was optional."
 -- Zot and Peabody, in ZOT! #1