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Greenplum gp_vmem_protect_limit configuration

We are doing a PoC by installing Greenplum on AWS environment. We have setup each of our segment servers as d2.8xlarge instance types which has 240 GB of RAM with no SWAP.

I am now trying to setup the gp_vmem_protect_limit using the formula mentioned in gpdb documents and the value is coming to 25600MB.

But in one of the Zendesk Notes it says that gp_vmem_protect_limit will be breached when "sessions executing on this segment are attempting together to use more than configured limit. " Does the segment in this text mean Segment Host or number of primary segments?

Also, with the Eager Free option being set I see that the memory utilization is very poor when running the TPC-DS benchmark with 5 concurrent users. I would like to improve the memory utilization of the environment and below are the other memory configurations

gpconfig -c gp_vmem_protect_limit -v 25600MB
gpconfig -c max_statement_mem -v 16384MB
gpconfig -c statement_mem -v 2400MB

Any suggestions?

Thanks, Jayadeep

Solution

  • There is a calculator for it!
    http://greenplum.org/calc/

    You should also add a swap file or disk. It is pretty easy to do in Amazon too. I would add at least a 4GB swap file to each host when you have 240GB of RAM.