Subject: Re: tg3 bad performance, lots of hardware interrupts
From: "Michael Chan" <mchan@broadcom.com>
To: "David Miller" <davem@davemloft.net>
cc: harald@iki.fi, linux-kernel@vger.kernel.org,
       netdev <netdev@vger.kernel.org>
In-Reply-To: <20080327.144925.196529669.davem@davemloft.net>
References: <alpine.DEB.1.00.0803271532570.30549@penti.org>
 <20080327.144925.196529669.davem@davemloft.net>
Date: Thu, 27 Mar 2008 17:01:38 -0800
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On Thu, 2008-03-27 at 14:49 -0700, David Miller wrote:
> From: Harald Hannelius <harald@iki.fi>
> Date: Thu, 27 Mar 2008 15:53:56 +0200 (EET)
> 
> > I experience a lot of hardware interrupts with a BCM5751 PCI-express NIC 
> > (tg3). modprobe tg3, ifconfig ethX up and friends makes the system 
> > unresponsive. Just having the interface up makes the system sluggish.
> > 

I just tested a similar NIC using the same kernel and driver, but I did
not notice anything unusual.  netperf gave me 941Mbps.

> > Onboard forcedeth works fine (with the same cable).
> > 
> > iperf gives me just 2Mbps on a 1Gbps ethernet. Load average near 1.0. top 
> > reports 40-50%hi (hardware interrupts) when generating traffic over that 
> > interface.

Can you look at /proc/interrupts to see roughly how many are reported
per second when link is down, link is up with no traffic, and with
traffic?

Finally, you can also try ethtool -t eth0 to see if it passes a simple
self test.

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