Lightboard Lessons: CPU Hyper-Threads and TMM

In this episode of Lightboard Lessons, Jason details how BIG-IP’s Traffic Management Microkernel (TMM) utilizes Intel’s Hyper-Threading Technology (on applicable platforms) and the impacts depending on the version of TMOS. In versions before 11.5, each hyper-thread has a separate TMM running. In versions 11.5 and later, TMM and control plane tasks are assigned to separate hyper-threads by default, a behavior we call HTSplit. This behavior is controlled by the scheduler.splitplanes.ltm database key.

Note: This video is a result of a great question by community member Aditya. You can read about the background here.

Resources

  • K15003: Data plane and control plane tasks use separate logical cores when the BIG-IP system CPU uses Hyper-Threading Technology
  • K23505424: Overview of the HTSplit feature
  • K14358: Overview of Clustered Multiprocessing (11.3.0 and later)
  • K10095: Error Message: Clock advanced by ticks
  • K16469: Certain BIG-IP ASM control plane processes are now pinned to the highest-numbered logical CPU core
Published Sep 06, 2017
Version 1.0
application delivery
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TMOS
  • dragonflymr's avatar
    dragonflymr
    Icon for Cirrostratus rankCirrostratus
    Sep 26, 2017

    Hi,

     

    I am back :-)

     

    Some more questions:

     

    HTSplit and vCMP - is same rule about even and odd virtual cores apply to vCMP guest? What when we have 1 vCPU vGuest?

     

    ASM - according to KB ASM is using highest numbered core for part of control plane tasks. Same rule about halting 80% of odd core still applies here - so ASM control plane processes will be throttled to 20% if even core is loaded over 80%?

     

    Is ASM really limited for those selected control plane task to one and only one core? I've seen configs where highest numbered core was almost constantly loaded 90-100% - I assume mainly by ASM control plane, if only one core can be dedicated to ASM what is an option in such case?

     

    Piotr

     

  • sk_330490's avatar
    sk_330490
    Icon for Nimbostratus rankNimbostratus
    Nov 17, 2017

    Does this cause packet drops, when we see those logs on /var/log/kern? I can see it our box, when we do load tests on certain VIPs and these logs start growing. And the application see timeouts from the VIP

     

  • JRahm's avatar
    JRahm
    Icon for Admin rankAdmin
    Nov 20, 2017

    you should not see drops from issues related to this message, it's just enforcing the throttle to make sure TMM is handling the load ok.