[Twisted-Python] Large file transfers

Donovan Baarda abo at minkirri.apana.org.au
Mon Jul 29 19:57:30 MDT 2002


G'day,

On Mon, Jul 29, 2002 at 10:35:59AM -0500, Glyph Lefkowitz wrote:
> 
> On Mon, 29 Jul 2002 12:35:31 +0300, Tommi Virtanen <tv at twistedmatrix.com> wrote:
> > On Fri, Jul 26, 2002 at 07:41:27AM -0500, Chris Armstrong wrote:
[...]

Does anyone else find it funny to have a discussion about the performance
problems of select/poll/whatever on a list devoted to a server framework
written in an (psedo-)interpreted scripting language :-)

> Asyncore has a great little comment about this:
> 
> # After a little research (reading man pages on various unixen, and
> # digging through the linux kernel), I've determined that select()
> # isn't meant for doing doing asynchronous file i/o.
> # Heartening, though - reading linux/mm/filemap.c shows that linux
> # supports asynchronous read-ahead.  So _MOST_ of the time, the data
> # will be sitting in memory for us already when we go to read it.
> 
> Hope this is enlightening.

I'm curious as to what this actually means. If I give an open file a fcntl()
to set it to non-blocking and use it in a select(), what happens? Do I get
undeterminite behaviour? Does the select always return the file immediately
as ready, only to have the read (sometimes) block?

-- 
----------------------------------------------------------------------
ABO: finger abo at minkirri.apana.org.au for more info, including pgp key
----------------------------------------------------------------------




More information about the Twisted-Python mailing list