Java / Java 17 Garbage Collection Interview Questions
What is the purpose of the -Xmx and -Xms flags?
-Xmx sets the maximum heap size the JVM is allowed to grow to, and -Xms sets the initial heap size allocated at startup - for example, -Xms512m -Xmx4g starts with a 512MB heap and allows growth up to 4GB.
If left unset, the JVM's ergonomics pick defaults based on available memory (or, inside a container, the cgroup memory limit) - often a fraction of that memory for -Xmx and a smaller fraction for -Xms.
Setting -Xms equal to -Xmx is a common production practice: it avoids the overhead of the heap resizing itself at runtime and gives more predictable, stable performance, at the cost of committing that memory up front even if it isn't immediately needed.
-Xmx controls:
Setting -Xms equal to -Xmx in production is commonly done to:
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