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Forum Discussion

dragonflymr's avatar
dragonflymr
Icon for Cirrostratus rankCirrostratus
Dec 08, 2015

iRule killing BIG-IP

Hi,   I have huge issue with iRule obviously killing BIG-IP 2000. In tests iRule logic works OK, but under load BIG-IP is overloaded.   Scenario:   BIG-IP no iRule, 30 to 40k concurrent con...
devops
irule optimization
iRules
LTM
performance
VernonWells's avatar
VernonWells
Icon for Employee rankEmployee
Dec 09, 2015

There is no easy way to answer the question "how much CPU time is devoted to the iRule, and how much is devoted to everything else happening with the connection handling". You may consider reaching out to your F5 Account team. The SE may be able to provide you with an estimate of the CPU budget available on your platform. From there, at least, you can estimate the total CPU cycles consumed by your rule (turn on timing for the rule by adding 

timing on
to the top of the rule, then use 
show ltm rule
to view the time consumed). The total consumption is

average-cycles * events-per-second

(In your case, an "event" is an HTTP Request). So, my results above show an average of 31.7k cycles. If there were 1000 requests/second, the estimated cpu cycles consumed would be 31.7M. If the total CPU budget on the platform is 100M cycles/second, then the rule, under that load, would consume ~30% of the available CPU (assuming the traffic is uniformly distributed across processing cores; that is, tmm instances).