Re: RFC: NAPI packet weighting patch

[Martin Josefsson <gandalf@xxxxxxxxxxxxxx>]

On Tue, 7 Jun 2005, jamal wrote:

> On Tue, 2005-07-06 at 14:06 +0200, Martin Josefsson wrote:
>
> > One thing that jumps to mind is that e1000 starts at lastrxdescriptor+1
> > and loops and checks the status of each descriptor and stops when it finds
> > a descriptor that isn't finished. Another way to do it is to read out the
> > current position of the ring and loop from lastrxdescriptor+1 up to the
> > current position. Scott Feldman implemented this for TX and there it
> > increased performance somewhat (discussed here on netdev some months ago).
> > I wonder if it could also decrease RX latency, I mean, we have to get the
> > cache miss sometime anyway.
> >
>
> The effect of Scotts patch was to reduce IO by amortizing it on the TX
> side. Are we talking about the same thing ? This was in the case of TX
> descriptor prunning?

Yes, that was for TX pruning.

> So it is possible that the e1000 is doing more than necessary share of
> IO on the receive side as well.

Yes, that's what I mean. Same thing but for RX but the question is how
much we would gain from it, we still need to touch the rx-descriptor
sooner or later. Would be worth a test.
My testsetup isn't in a working condition right now, Robert?

/Martin