High CPU load on 4506Sup IV - What is PM Callback?

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Dec 16th, 2007
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We have two 4506 chassis's on our campus network and are seeing high CPU loads. We are running 12.2.25EWA12 code (just upgraded from EWA11) and the load on our core1 switch is ~65-70%, with the core2 switch at about 45-50%.


The odd thing is that when we reloaded core1, then core2, the cpu load shifted to core2. We run STP and HSRP, but standby groups are working fine (core 1 active for all instances/groups) and no STP loops show (topologies are stable).


In looking at the CPU processes (show process cpu | exc 0.00) the following main items are consuming the CPU:


29 71968 9750 7381 13.21% 14.47% 11.42% 0 Cat4k Mgmt HiPri

30 27888 2905 9600 6.68% 5.53% 4.19% 0 Cat4k Mgmt LoPri

49 98760 2648 37296 18.58% 22.41% 17.26% 0 Spanning Tree

99 199136 1720 115776 57.15% 50.09% 35.87% 0 PM Callback


In looking at the details, the "PM Callback" process is consuming CPU, and this is the process that shifted load from core1 to core2 after the reload.


(Meaning Callback was 40-50% on core1, then after reload order aboe, core2 is now at 40-50%, with core1 around 5% for Call Back process)


Any idea what the PM Callback process is, and more importantly, what is causing the load and how can I reduce it?


Thanks,


-Scott

















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Anonymous (not verified) Tue, 12/25/2007 - 06:34
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There is no much information available about PM. As far I know PM process is invoked whenever a New VLAN is cretaed . Becuase spanning is created for each VLAN instance. This takes lot of CPU for multiple VLANs.

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