kern/31940: nge gigabit adapter link reset and slow transfert

[lukem.freebsd at cse.unsw.edu.au]

The following reply was made to PR kern/31940; it has been noted by GNATS.

From: lukem.freebsd at cse.unsw.edu.au
To: freebsd-gnats-submit at FreeBSD.org, fabien.thomas at wanadoo.fr,
	dwmalone at maths.tcd.ie
Cc:  
Subject: Re: kern/31940: nge gigabit adapter link reset and slow transfert
Date: Tue, 2 Nov 2004 10:51:59 +1100 (EST)

 I am using 5.2.1, rather than 4.4, but I have found a bug which could be 
 causing this. I have mailed freebsd-net but they don't seem interested. 
 The problem is that the receive DMA ring is longer than the IP queue, such 
 that if more packets are received in the interrupt than fit in the IP 
 queue, packets are dropped.
 
 Since the default IP queue length is 50 packets, and the interrupt holdoff 
 time is 100uS, you can only really expect to get 500kpps, which is not 
 much for a gigabit ethernet card.
 
 You can fix by increasing the ip queue length constant. (make it >= 128)
 
 -- 
 Luke