我有一个在 docker 容器中运行的 java 应用程序（JDK13）。最近我将应用程序迁移到 JDK17（OpenJDK17），发现 docker 容器的内存使用量逐渐增加。
在调查期间，我发现“可维护性内存类别”NMT 不断增长（每小时 15mb）。我检查了页面https://docs.oracle.com/en/java/javase/17/troubleshoot/diagnostic-tools.html#GUID-5EF7BB07-C903-4EBD-A9C2-EC0E44048D37但那里没有提到这个类别。
谁能解释这个可维护性类别是什么意思以及什么会导致这种逐渐增加？与 JDK13 相比，还有一些额外的新内存类别。也许有人知道我可以在哪里阅读有关它们的详细信息。
这是命令的结果jcmd 1 VM.native_memory summary
Native Memory Tracking:
(Omitting categories weighting less than 1KB)
Total: reserved=4431401KB, committed=1191617KB
- Java Heap (reserved=2097152KB, committed=479232KB)
(mmap: reserved=2097152KB, committed=479232KB)
- Class (reserved=1052227KB, committed=22403KB)
(classes #29547)
( instance classes #27790, array classes #1757)
(malloc=3651KB #79345)
(mmap: reserved=1048576KB, committed=18752KB)
( Metadata: )
( reserved=139264KB, committed=130816KB)
( used=130309KB)
( waste=507KB =0.39%)
( Class space:)
( reserved=1048576KB, committed=18752KB)
( used=18149KB)
( waste=603KB =3.21%)
- Thread (reserved=387638KB, committed=40694KB)
(thread #378)
(stack: reserved=386548KB, committed=39604KB)
(malloc=650KB #2271)
(arena=440KB #752)
- Code (reserved=253202KB, committed=76734KB)
(malloc=5518KB #23715)
(mmap: reserved=247684KB, committed=71216KB)
- GC (reserved=152419KB, committed=92391KB)
(malloc=40783KB #34817)
(mmap: reserved=111636KB, committed=51608KB)
- Compiler (reserved=1506KB, committed=1506KB)
(malloc=1342KB #2557)
(arena=165KB #5)
- Internal (reserved=5579KB, committed=5579KB)
(malloc=5543KB #33822)
(mmap: reserved=36KB, committed=36KB)
- Other (reserved=231161KB, committed=231161KB)
(malloc=231161KB #347)
- Symbol (reserved=30558KB, committed=30558KB)
(malloc=28887KB #769230)
(arena=1670KB #1)
- Native Memory Tracking (reserved=16412KB, committed=16412KB)
(malloc=575KB #8281)
(tracking overhead=15837KB)
- Shared class space (reserved=12288KB, committed=12136KB)
(mmap: reserved=12288KB, committed=12136KB)
- Arena Chunk (reserved=18743KB, committed=18743KB)
(malloc=18743KB)
- Tracing (reserved=32KB, committed=32KB)
(arena=32KB #1)
- Logging (reserved=7KB, committed=7KB)
(malloc=7KB #289)
- Arguments (reserved=1KB, committed=1KB)
(malloc=1KB #53)
- Module (reserved=1045KB, committed=1045KB)
(malloc=1045KB #5026)
- Safepoint (reserved=8KB, committed=8KB)
(mmap: reserved=8KB, committed=8KB)
- Synchronization (reserved=204KB, committed=204KB)
(malloc=204KB #2026)
- Serviceability (reserved=31187KB, committed=31187KB)
(malloc=31187KB #49714)
- Metaspace (reserved=140032KB, committed=131584KB)
(malloc=768KB #622)
(mmap: reserved=139264KB, committed=130816KB)
- String Deduplication (reserved=1KB, committed=1KB)
(malloc=1KB #8)
关于增加部分内存的详细信息是：
[0x00007f6ccb970cbe] OopStorage::try_add_block()+0x2e
[0x00007f6ccb97132d] OopStorage::allocate()+0x3d
[0x00007f6ccbb34ee8] StackFrameInfo::StackFrameInfo(javaVFrame*, bool)+0x68
[0x00007f6ccbb35a64] ThreadStackTrace::dump_stack_at_safepoint(int)+0xe4
(malloc=6755KB type=Serviceability #10944)
2022-01-17 更新#1：
感谢@Aleksey Shipilev 的帮助！我们能够找到导致问题的地方，这与许多 ThreadMXBean#.dumpAllThreads 调用有关。这是 MCVE，Test.java：
运行：
java -Xmx512M -XX:NativeMemoryTracking=detail Test.java
并定期检查可用性类别的结果
jcmd YOUR_PID VM.native_memory summary
测试java：
import java.lang.management.ManagementFactory;
import java.lang.management.ThreadInfo;
import java.lang.management.ThreadMXBean;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
public class Test {
private static final int RUNNING = 40;
private static final int WAITING = 460;
private final Object monitor = new Object();
private final ThreadMXBean threadMxBean = ManagementFactory.getThreadMXBean();
private final ExecutorService executorService = Executors.newFixedThreadPool(RUNNING + WAITING);
void startRunningThread() {
executorService.submit(() -> {
while (true) {
}
});
}
void startWaitingThread() {
executorService.submit(() -> {
try {
monitor.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
});
}
void startThreads() {
for (int i = 0; i < RUNNING; i++) {
startRunningThread();
}
for (int i = 0; i < WAITING; i++) {
startWaitingThread();
}
}
void shutdown() {
executorService.shutdown();
try {
executorService.awaitTermination(5, TimeUnit.SECONDS);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public static void main(String[] args) throws InterruptedException {
Test test = new Test();
Runtime.getRuntime().addShutdownHook(new Thread(test::shutdown));
test.startThreads();
for (int i = 0; i < 12000; i++) {
ThreadInfo[] threadInfos = test.threadMxBean.dumpAllThreads(false, false);
System.out.println("ThreadInfos: " + threadInfos.length);
Thread.sleep(100);
}
test.shutdown();
}
}
