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

max ulidtko ulidtko at gmail.com
Mon Jan 10 01:00:06 CET 2011


On Sun, 9 Jan 2011 11:17:40 -0800, Guido van Rossum wrote:
| Isn't that just shutil.copyfileobj()?
|

This function has two drawbacks. First, it copies until EOF, and has no
possibility to copy exactly N bytes from source fd (say, opened socket).
This is the reason why I (re)wrote my custom copying function - to allow
that.

The second drawback is not using huge performance bonus achievable with
sendfile(2) syscall on some unices and TransmitFile() on win32. It
allows for sending and receiving files at ethernet speeds with no CPU
load at all, because no memory copying occurs (and no Python wrapper
objects would be created for the buffers, no heap allocation, etc). All
needed I/O requests are handled inside the kernel without a single
copying of data.

Thus for e.g. FTP servers using this syscall became a standard. It would
be good if Python supported it.

P.S.
There seems to be a package which enables the sendfile support for
Linux, FreeBSD and AIX, <http://pypi.python.org/pypi/py-sendfile/>.
Though it's available only for 2.x.

Hopefully I'll end up with a patch soon.


-------
Regards,
max ulidtko



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