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answ161's avatar
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Aug 23, 2023

Higher Monitor CPU Usage in v16

Hi All,

After an attempted upgrade of our production BIG-IPs (i4600 HA pair) from v14 to v16 earlier this year that required a rollback due to high CPU utilization, I have been doing testing on some VEs and noticed that v16 has about 15% higher CPU utilization just from monitors.

The Setup: only LTM and GTM are provisioned, but no GTM usage.  I copied config from production units to the test VEs, excluding VIP and SNAT objects.  The LTM has around 1200 pools configured, 2-4 members in each pool, 1-2 monitors on each pool with most only having 1 monitor.  The majority of the montitors are HTTP/HTTPS, which I understand do use more CPU than something like TCP (

However, it seems odd that monitors on v16 would use almost 15% more CPU than prior versions.  I was running v14 as a baseline, noticed nominally higher (~1-3%) CPU in v15, and around 15% in v16.  Has anyone else noticed this, or able to provide an explanation?

Below are some screenshots of the CPU graph on the VE when switching betwen v14.1.4.6,, and  The first is a 24-hour window, and the second two are 4-hour window graphs.



7 Replies

  • Hi holge, no updates yet.  I'm going to be opening a case on this with F5 support today.  I'll keep updates posted in here as I learn more.  During testing of a few different versions, I also see the same behavior in 16.1.4.  Given some time to sit over the past week, average CPU is 18% higher compared to an identical VE running

    • AndreiHurmuz's avatar
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      Hi answ161 

      did you get any resolution on that issue? We are experimenting the same problem with v16, as of now 4 systems have increased CPU usage since the update, VE and HW Big-Ip. 

      Many thanks in advance!


      • answ161's avatar
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        Hi AndreiHurmuz,

        In my configuration, F5 support helped to determined that LDAP monitors in v16 are the cause of higher CPU utilization.  Removing LDAP monitors caused CPU to drop by about 15%.  However, the reason why LDAP monitors use more CPU in v16 is not known.  

        This may not be the cause in your case, but top output should confirm this. 

  • holge's avatar
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    Hello @answ161 , 

    Any update on this one? We have a very similar setup and experiencing very similar outcome after upgrading to