Re: [PATCH] async poll for 2.5

[Mark Mielke <mark@mark.mielke.cc>]

On Wed, Oct 16, 2002 at 11:15:50AM -0700, John Gardiner Myers wrote:
> Davide Libenzi wrote:
> >This because you have to consume the I/O space to push the level to 0 so
> >that a transaction 0->1 can happen and you can happily receive your
> >events.
> This is done with something like:
> for (;;) {
>     fd = event_wait(...);
>     while (do_io(fd) != EAGAIN);
> }
> Trying to do at once as much work as one can on a given fd helps keep 
> that fd's context information in cache.  If one needs to have the fd 
> yield the CPU in order to reduce system latency, one generates a 
> user-mode event.

Not to enter into any of the other discussions on this issue, I wouldn't
usually do what you suggest above. Sure, for operations like accept() that
are inherently inefficient, I would loop until EAGAIN, but if I did I
a recv() or read() of 2K, and I only received 1K, there is no reason why
another system call should be invoked on the resource that likely will not
have any data ready.

mark

-- 
mark@mielke.cc/markm@ncf.ca/markm@nortelnetworks.com __________________________
.  .  _  ._  . .   .__    .  . ._. .__ .   . . .__  | Neighbourhood Coder
|\/| |_| |_| |/    |_     |\/|  |  |_  |   |/  |_   | 
|  | | | | \ | \   |__ .  |  | .|. |__ |__ | \ |__  | Ottawa, Ontario, Canada

  One ring to rule them all, one ring to find them, one ring to bring them all
                       and in the darkness bind them...

                           http://mark.mielke.cc/