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  • 1.  Difference between %RDY & %LAT_C

    Posted May 09, 2012 11:49 AM

    %RDY gets a lot of publicity, and is shown in the cpu panel of esxtop by default, but %LAT_C has to be enabled. From the description in the esx4.1 resource guide, they seem very similar.

    -----------

    %RDY Percentage of time the resource pool, virtual machine, or world was ready to run, but was not

    provided CPU resources on which to execute.

    %LAT_C Percentage of time the resource pool or world was ready to run but was not scheduled to run because

    of CPU resource contention.

    -----------

    Although I see a lot more %LAT_C than %RDY.

    Can anyone explain it in more detail and offer examples?

    Cheers.



  • 2.  RE: Difference between %RDY & %LAT_C

    Posted May 09, 2012 01:27 PM

    Hi

    As far as i've always understood it, %ready is pretty straight forward as the time a process is ready to do something but there is no cpu resources available to do the processing

    %lat_c is applicable for a number of things like as it says in the example a resource pool and if there are say ten machines in a resource pool that are waiting on cpu resource for varying times, then this is averaged into a percentage and that is the latency you are getting in waiting for the CPU.

    But that's my understanding and I'm sure some guru will tell em i'm wrong.

    Every day's a school day :smileygrin:

    Gregg



  • 3.  RE: Difference between %RDY & %LAT_C

    Posted May 11, 2012 10:59 AM

    Hi Gregg.

    Thanks for the reply.

    I'm still not too sure of the difference.

    I haven't heard much on %LAT_C, but it sounds like it's a true indication of oversubscription, whereas %RDY may indicate 1 core free but a 4vCPU VM waiting for more cores to free up.

    Any insight to your %LAT_C values?

    If i make it to VMworld, i might see if i can ask the experts there.



  • 4.  RE: Difference between %RDY & %LAT_C

    Posted May 12, 2012 02:55 PM

    daunce wrote:

    whereas %RDY may indicate 1 core free but a 4vCPU VM waiting for more cores to free up.

    There is another counter to watch for this, called %CSTP, where a multi vCPU has to wait for physical cores to be available.