Re: [PATCH] async poll for 2.5

From: Mark Mielke (mark@mark.mielke.cc)
Date: Wed Oct 16 2002 - 15:06:20 EST

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 

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