InitiatingHeapOccupancyPercent tuning parameter value modification ( 75 to 30 )from 7.0.1 version to 7.8.0 in G1GC for elasticsearch

Elastic Stack Elasticsearch
1

"InitiatingHeapOccupancyPercent" parameter is set to 75 for elasticsearch 7.0.1, which is now updated to 30. Please state the reason why was it changed and what effect did it have.

7.0.1 version's jvm.options snippet:

## G1GC Configuration
# NOTE: G1GC is only supported on JDK version 10 or later.
# To use G1GC uncomment the lines below.
# 10-:-XX:-UseConcMarkSweepGC
# 10-:-XX:-UseCMSInitiatingOccupancyOnly
# 10-:-XX:+UseG1GC
# 10-:-XX:InitiatingHeapOccupancyPercent=75

7.8.0 version's snippet:

## G1GC Configuration
# NOTE: G1 GC is only supported on JDK version 10 or later
# to use G1GC, uncomment the next two lines and update the version on the
# following three lines to your version of the JDK
# 10-13:-XX:-UseConcMarkSweepGC
# 10-13:-XX:-UseCMSInitiatingOccupancyOnly
14-:-XX:+UseG1GC
14-:-XX:G1ReservePercent=25
14-:-XX:InitiatingHeapOccupancyPercent=30

Thanks in advance

2

Elasticsearch 7.8 by default uses G1GC which required different settings compared to CMS GC which is used in Elasticsearch 7.1.

3

We are using java 11, so the default GC still remains as CMS only.
But, we have to use G1 as the garbage collector. For achieving this, we have changed the jvm.options to enable G1GC for java 11. Please confirm, if we can still use the same configuration of G1GC for java 11 as well.

Thanks in advance.

4

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