Higher Monitor CPU Usage in v16

Question

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.&nbsp; I copied config from production units to the test VEs, excluding VIP and SNAT objects.&nbsp; 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.&nbsp; The majority of the montitors are HTTP/HTTPS, which I understand do use more CPU than something like TCP (https://my.f5.com/manage/s/article/K42421592).However, it seems odd that monitors on v16 would use almost 15% more CPU than prior versions.&nbsp; I was running v14 as a baseline, noticed nominally higher (~1-3%) CPU in v15, and around 15% in v16.&nbsp; 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, 15.1.9.1, and 16.1.3.3.&nbsp; The first is a 24-hour window, and the second two are 4-hour window graphs.&nbsp;&nbsp;

answ161 · Answer

Hi holge, no updates yet.&nbsp; I'm going to be opening a case on this with F5 support today.&nbsp; I'll keep updates posted in here as I learn more.&nbsp; During testing of a few different versions, I also see the same behavior in 16.1.4.&nbsp; Given some time to sit over the past week, average CPU is 18% higher compared to an identical VE running 14.1.4.6.

answ161 · Answer

Hi&nbsp;AndreiHurmuz,In my configuration, F5 support helped to determined that LDAP monitors in v16 are the cause of higher CPU utilization.&nbsp; Removing LDAP monitors caused CPU to drop by about 15%.&nbsp; However, the reason why LDAP monitors use more CPU in v16 is not known.&nbsp;&nbsp;This may not be the cause in your case, but top output should confirm this.&nbsp;

holge · Answer

Hi&nbsp;AndreiHurmuz&nbsp;I worked with F5 support on the issue. The comment from them was;Yes, a some CPU usage increase after upgrading to a later major software release is expected due to additional features in the new software version. However, this should not affect production traffic. If it does, we have to review the configuration and adjust things until we get this under control.So some CPU rise is expected. We needed to look at cleaning up our config. Some standouts aside from the LDAP monitors mentioned by&nbsp;answ161&nbsp; is halfopen monitors. We had a lot of them and they put load on CPU. Also if you have a lot of pool members that are down, the system is constantly waiting for responses from those members.Cheers

mohamed_ahmed_kansoh · Answer

Hello&nbsp;answ161&nbsp;,&nbsp;I believe this should be escalated to F5 Support , you may need a hotfix for an undefined BUG.&nbsp;anyway have a look in this BUG&nbsp; https://cdn.f5.com/product/bugtracker/ID544902.html&nbsp;, it affects all of your upgraded versions for ( TCP_half_open ) monitor if you use it ,&nbsp;

holge · Answer

Hello&nbsp;@answ161&nbsp;,&nbsp;Any update on this one? We have a very similar setup and experiencing very similar outcome after upgrading to 16.1.3.3Thanks

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Higher Monitor CPU Usage in v16

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