RE: excessive interrupts on network cards

[Chris Newton]

Yea, it is a single port card... I had meant to mention that in the email I 
sent out...  ie: that it wasn't reporting correctly... but, I didnt really 
think it was related, since the eepro was doing the same thing.

  As for comparing with ifconfig, I ran 'watch 1 ifconfig -a', and sure 
enough, I have about ~7000-7500 packets coming in right now.  And, the 
'procinfo -D', reports ~21000-22000 interrupts per second.

  Other sources I have used to confirm packet rate... include output from 
'sniffer', a flow generator that was monitoring that link, and the hub this 
machine is plugged into.

  the hub has 3 active ports.. port 1 is one side of our internet conenction 
(out to our provider), port 2 was from the hub over to our main router... port 
3 is a mirror of the IN on port 1 and the OUT on port 2 to port 3.  Comparing, 
and verifying, showed port 3 getting 10K packets (this afternoon, which 
obviously drops at night, which it is here now), and down to 7K now.

Chris

>===== Original Message From Andrew Morton <[e-mail]> =====
>Chris Newton wrote:
>>
>> Hi,
>>
>>   I 'think' the number of interrupts being generated for the network 
traffic I
>> monitor, is excessive.  Having talked quikly with Donald Becker, he 
indicated
>> that I should be seeing a little less than the number of RX/TX packets/s on 
a
>> wire, in terms of interrupts/s.  That, however, is not what I am seeing.  I 
am
>> seeing 3 times as many interrupts/s as I am seeing packets/s.
>>
>>   I have used three network devices to look at the stream I am monitoring, 
and
>> it is usually aorund 5K packet/s IN, and 5K out, fed full duplex into a 
single
>> 3Com 3c982 (2.4.10 kernel reports that anyways).  However, watching:
>
>3c982 is a dual-port server NIC.  Is your card dual-port?  If not, it's 
probably
>a 3c980, and I goofed :)
>
>>  'procinfo -D', reports on the order of 30,000 interrupts per second.
>
>That does sound rather high.  You should compare the interrupt rate
>with the packet rate from `ifconfig' or /proc/net/dev.
>
>Normally, 3c59x will show approx three Tx packets per interrupt
>and one Rx packet per interrupt.  It varies with workload, but
>it tends to vary in the "good" direction - at higher packet
>rates, we do more work in a single interrupt and the interrupt-per-packet
>rate falls.