Why Upgrading to JDK 17 with ZGC Is Essential for Low‑Latency Services

Background TL;DR

Garbage‑collector pause times are a critical pain point for services that require real‑time response; traditional collectors like CMS and G1 can pause for tens to hundreds of milliseconds, and tuning them is difficult. ZGC, introduced experimentally in JDK 11 and production‑ready in JDK 15, solves this problem, and JDK 17 is the first LTS version that fully supports it.

Why Upgrade to JDK 17

Supports heap sizes from 8 MB to 16 TB

Maximum GC pause of 10 ms

Throughput may drop up to 15 % in worst cases (often less)

Low‑latency business needs demand millisecond‑level GC pauses. In Meituan’s Zeus service, ZGC reduced TP999 latency by 12–142 ms (18‑74 %) and TP99 by 5–28 ms (10‑47 %).

Additional reasons to upgrade:

Spring Boot 3 requires JDK 17

JIT compiler improvements

New language features such as sealed classes, pattern matching, records

Enhanced security fixes and mechanisms

Applicable Scenarios

Gateway services

Web APIs

Not recommended for batch jobs, scheduled tasks, or CPU‑intensive workloads.

Before‑After Comparison

Environment: 4‑core CPU, 6 GB RAM.

GC Time Comparison

ZGC achieves sub‑millisecond GC pauses, keeping JVM‑induced latency under 1 ms.

CPU Usage Comparison

Running the same code on JDK 17 consumes 10‑20 % more CPU than JDK 8.

Upgrade Method

1. Install JDK 17

# Ubuntu installation
sudo apt install openjdk-17-jdk

# Docker base images
docker pull openjdk:17-slim
docker pull openjdk:17-jdk-oraclelinux7
FROM openjdk:17-slim

2. JVM Parameter Tuning

--add-opens=java.base/java.lang=ALL-UNNAMED \
-Xms1500m -Xmx1500m \
-XX:ReservedCodeCacheSize=256m \
-XX:InitialCodeCacheSize=256m \
-XX:+UnlockExperimentalVMOptions \
-XX:+UseZGC \
-XX:ConcGCThreads=1 -XX:ParallelGCThreads=2 \
-XX:ZCollectionInterval=30 -XX:ZAllocationSpikeTolerance=5 \
-XX:+UnlockDiagnosticVMOptions -XX:-ZProactive \
-Xlog:safepoint,classhisto*=trace,age*,gc*=info:file=/opt/gc-%t.log:time,tid,tags:filecount=5,filesize=50m \
-XX:+HeapDumpOnOutOfMemoryError \
-XX:HeapDumpPath=/opt/errorDump.hprof

Parameter Explanation

References

https://tech.meituan.com/2020/08/06/new-zgc-practice-in-meituan.html

https://tech.dewu.com/article?id=59