rezasafi commented on issue #23767: [SPARK-26329][CORE] Faster polling of 
executor memory metrics.
URL: https://github.com/apache/spark/pull/23767#issuecomment-478039936
 
 
   > It is not sending a new heartbeat. It is changing the information sent in 
the existing heartbeat.
   
   In Execuor.scala I can see this:
   
   `heartbeater.start()
   
     metricsPoller.start()`
   So I think it is introducing a new thread similar to heartbeater.  It is 
just on the driver that the change is using the original heatbeater.
   
   > That said, you could still ask what's the effect on the performance of the 
executors, and what's a reasonable polling frequency. Its impossible to answer 
that for all cases, as it'll depend on the workload, but still it is a good 
idea for us to have some measurement at least.
   
   yeah, It is obvious that we can't test for every usecase/workload, but some 
analysis at least is good. I don't know you guys may have already done that. 
Unfortunately I wasn't involved in the whole process. I think based on the 
discussions that we had with @edwinalu, she did something like that  for their 
pr at the time. For procfsbased metrics also some analysis was done and it was 
noticed that the overhead isn't significant.  
   
   Saying that,  in general it seems that community doesn't believe to do 
overhead/performance analysis for features and it is common practice to make 
the feature configurable and leave the analysis to the user. So with that in 
mind this change is ok as it is.
   

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