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High Interrupt Utilization for AP

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Aug 14th, 2006
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I have noticed that that the CPU utilization for the AP is quite high at 61%. Breaking this 61/60% down:


Total CPU Utilization: 61%

Process Utilization: 1%

Interrupt Utilization: 60%


Can someone advise why I am see such a high interrupt utilization? What is causing this. The AP is running 123-7.JA2.





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jackyoung Mon, 08/14/2006 - 22:08
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Could you advise where do you get the interrupt utilization figure ? The attached file do not show this value. Is it a completed capture ?


Cannot find similiar info. in CCO. Below is link w/ similiar sympton but it is a router. You can check it as reference.


http://www.cisco.com/en/US/products/hw/iad/ps397/products_tech_note09186a00800a73e9.shtml


Try to isolate the problem by disconnect all users, it the loading is still high, there may be an issue in the AP. If not, it may the user traffic cause this.


Hope this helps.

pppyyyppp Mon, 08/14/2006 - 22:57
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show proc cpu

CPU utilization for five seconds: 61%/60%; one minute: 61%; five minutes: 61%


The above value 61%/60% show that the processor utilization is 1% and interrupt utilization is 60%. This is how I get the value.


Anyone has better advice and thanks.

pppyyyppp Mon, 08/14/2006 - 23:11
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Can constant polling at 10 sec interval caused this high interrupt utilization issue.

jackyoung Mon, 08/14/2006 - 23:29
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Thanks for clarification. Do you mean an external polling to the AP ? If yes, try to disable the polling and what do you polling from the router. If there is non-stop polling (e.g. 10 sec not enough to polling all info.) then it may be the reason. Just a wild guess.


And, where do you polling to ? To the console port, LAN port or wireless connection ?


Check another doc. for high interrupt but for router too....


http://www.cisco.com/en/US/products/hw/routers/ps359/products_tech_note09186a00801c2af0.shtml


pppyyyppp Mon, 08/14/2006 - 23:47
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I have polled some OID from the AP (not router) at a frequency of 5 to 10sec. Not sure if this so frequent snmp polling result in high interrupt utilization.


Can anyone advise me.

jackyoung Tue, 08/15/2006 - 00:05
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The best way is to try to disable the polling for a few mins. to test it.

pppyyyppp Tue, 08/15/2006 - 00:11
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I have clear the counter 30 minutes ago, the following show high packet count (traffic) can this explain for the high cpu utilization:


Dot11Radio0 is up, line protocol is up

Hardware is 802.11G Radio, address is 0013.6049.12c0 (bia 0013.6049.12c0)

MTU 1500 bytes, BW 54000 Kbit, DLY 1000 usec,

reliability 255/255, txload 62/255, rxload 1/255

Encapsulation ARPA, loopback not set

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:11, output 00:00:00, output hang never

Last clearing of "show interface" counters 00:24:16

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 4

Queueing strategy: fifo

Output queue: 0/30 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 13270000 bits/sec, 1117 packets/sec

196 packets input, 31434 bytes, 0 no buffer

Received 45 broadcasts, 0 runts, 0 giants, 3 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 input packets with dribble condition detected

1594425 packets output, 2368356603 bytes, 0 underruns

53 output errors, 0 collisions, 0 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

Dot11Radio1 is up, line protocol is up

Hardware is 802.11A Radio, address is 0013.6066.d2c0 (bia 0013.6066.d2c0)

MTU 1500 bytes, BW 54000 Kbit, DLY 1000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:01:25, output 00:00:00, output hang never

Last clearing of "show interface" counters 00:24:16

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/30 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 366000 bits/sec, 579 packets/sec

17 packets input, 3366 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 3 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 input packets with dribble condition detected

823679 packets output, 64671823 bytes, 0 underruns

96 output errors, 0 collisions, 0 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

jackyoung Tue, 08/15/2006 - 01:26
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You are right. The packet seems originate from the router to somewhere, I believe it is the device that continue to poll the AP. Did you try to disable the polling process to prove it ?

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