Re: rbuf starvation in the iwn driver

[Sverre Froyen <sverre%viewmark.com@localhost>]

On Tue April 6 2010 06:26:10 Manuel Bouyer wrote:
...
> What is doing this driver looks somewhat wrong to me.
> It can use its rbufs as external mbuf storage, and pass this to the network
> stack, as long as there's enough free rbufs. When the number of free rbufs
> is below the limit, it should stop giving them to the network stack,
> and copy the received data to a ordinary mbuf cluster instead.
> See for example if_nfe.c:

I've been looking at the iwn_rx_done code to see how I can fix this. One option 
is to use the code from iwn_rx_intr in if_iwn.c rev 1.32 (I presume I can 
figure out the needed bus_dmamap changes by looking at if_nfe.c).

However, it looks like the current OpenBSD and FreeBSD drivers do not use 
private storage. FreeBSD just gets an mbuf cluster from m_getjcl and OpenBSD 
uses MCLGETI. Is this an option for NetBSD? Why was private storage used in 
the first place? For speed reasons? Damien Bergamini warned me there would 
likely be alignment issues.

Thanks,
Sverre