Re: [lwip-users] performance

[K.J. Mansley]

On Thu, 2004-07-29 at 11:54, Sam Jansen wrote:
> On Thu, 2004-07-29 at 21:50, K.J. Mansley wrote:
> > On Wed, 2004-07-28 at 22:53, Sam Jansen wrote:
> > > Where lwIP doesn't shine is when the network coniditions are not so 
> > > perfect. It's my belief that the granularity of the timers hurts it 
> > > here, having to wait a minimum 500ms for a retransmit timeout can be 
> > > seriously detrimental to TCP performance.
> > 
> > That is, I think, something which is common to all (most?) TCPs, not
> > just lwIP.  It's also something that would be easy to change.  I agree
> > that, if TCP was being specified now, it would be unlikely that the
> > retransmit timer would have such a long timeout.
> 
> Maybe in the 1980's.
> 
> If we look at FreeBSD as a shining example of a BSD TCP implementation,
> you'll find that the timer granularity by default is 10ms. This is set
> by the HZ value which is specified in the kernel configuration. With a
> HZ of 100 (the default), the softclock() function is called 100 times a
> second, which will check the timers.

But that updates the frequency with which it is checked, not the value
of the timeout itself?  i.e. It will be more accurately 500ms, but still
500ms.

Kieran