我有一个小应用程序,它分配了大约25000个线程,然后释放它们。 当线程被释放时,即使在所有线程都退出之后,应用程序的内存消耗也会上升并保持高水平。
顶部看起来像这样:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
9133 root 20 0 22.601g 8.612g 12080 S 0.0 9.1 1:18.61 java
虽然 jmap -heap 如下所示:
Attaching to process ID 9133, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.66-b17
using thread-local object allocation.
Parallel GC with 18 thread(s)
Heap Configuration:
MinHeapFreeRatio = 40
MaxHeapFreeRatio = 100
MaxHeapSize = 1073741824 (1024.0MB)
NewSize = 104857600 (100.0MB)
MaxNewSize = 104857600 (100.0MB)
OldSize = 968884224 (924.0MB)
NewRatio = 2
SurvivorRatio = 8
MetaspaceSize = 21807104 (20.796875MB)
CompressedClassSpaceSize = 1073741824 (1024.0MB)
MaxMetaspaceSize = 1073741824 (1024.0MB)
G1HeapRegionSize = 0 (0.0MB)
Heap Usage:
PS Young Generation
Eden Space:
capacity = 78643200 (75.0MB)
used = 1572864 (1.5MB)
free = 77070336 (73.5MB)
2.0% used
From Space:
capacity = 13107200 (12.5MB)
used = 0 (0.0MB)
free = 13107200 (12.5MB)
0.0% used
To Space:
capacity = 13107200 (12.5MB)
used = 0 (0.0MB)
free = 13107200 (12.5MB)
0.0% used
PS Old Generation
capacity = 968884224 (924.0MB)
used = 1264416 (1.205841064453125MB)
free = 967619808 (922.7941589355469MB)
0.13050227970271916% used
808 interned Strings occupying 54648 bytes.
据我所知,jmap报告中没有任何内容可以解释top报告的8.612g。
Java版本是oracle 1.8.0_66
该应用程序在Red Hat Enterprise Linux Server 7.1(Maipo)上运行。
该应用程序的代码如下:
import java.util.*;
import java.util.concurrent.atomic.AtomicInteger;
public class WaitTest {
static AtomicInteger ai = new AtomicInteger(0);
public static void main(String[] args) {
List<WaitingThread> threads = new LinkedList<>();
while (true) {
System.out.println("number of threads: " + ai.get());
String s = System.console().readLine();
if (s == null)
System.exit(0);
s = s.trim();
if (s.isEmpty())
continue;
char command = s.charAt(0);
if (command != '+' && command != '-') {
System.out.println("+ or - please");
continue;
}
String num = s.substring(1);
int iNum;
try {
iNum = Integer.parseInt(num.trim());
} catch (Exception ex) {
System.out.println("valid number please");
continue;
}
if (command == '+') {
for (int i = 0; i < iNum; i++) {
WaitingThread t = new WaitingThread();
t.start();
threads.add(t);
}
}
if (command == '-') {
Set<WaitingThread> threadsToJoin = new HashSet<>();
for (Iterator<WaitingThread> it = threads.iterator(); it.hasNext(); ) {
if (iNum > 0) {
WaitingThread t = it.next();
threadsToJoin.add(t);
synchronized (t.lock) {
t.lock.notify();
}
it.remove();
iNum--;
} else
break;
}
for (WaitingThread t : threadsToJoin)
try {
t.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.gc();
}
}
static class WaitingThread extends Thread {
public final Object lock = new Object();
@Override
public void run() {
ai.incrementAndGet();
try {
deepStack(200);
} catch (InterruptedException ex) {
} catch (Exception ex) {
System.out.println("exception in thread " + Thread.currentThread().getName() + ", " + ex.getMessage());
} finally {
ai.decrementAndGet();
}
}
private void deepStack(int depth) throws InterruptedException {
if (depth == 0) {
synchronized (lock) {
lock.wait();
}
} else
deepStack(depth - 1);
}
}
}
答案 0 :(得分:0)
在列表变量cv::Point2d pp(u0, v0);
cv::Mat R, t, mask;
cv::Mat E = cv::findEssentialMat(points1, points2, focal, pp, cv::RANSAC, 0.999, 1.0, mask);
cv::recoverPose(E, points1, points2, R, t);
中的命令“+”期间是否首先创建所有线程,这些命令永远不会超出范围?这意味着链表持有对所有线程的引用,并且在'threads'
退出之前不会进行垃圾回收。此外,它是possible that the LinkedList itself is leaking memory。即使这不是问题,您也应该考虑using an ArrayList instead of a LinkedList。
此外,这是另一个问题finding memory leaks in Java。
答案 1 :(得分:0)
应用程序内存仅与堆大小松散耦合。当GC运行并清理时,它会清理堆,而不是系统内存。实际上,JVM甚至可能不会进行系统调用以减少系统内存,即使它经常释放堆空间。
答案 2 :(得分:0)
每个线程都需要一个堆栈(已分配的内存),它不是java堆的一部分。
堆栈的默认大小取决于jvm版本,操作系统等。
您可以使用-Xss jvm参数进行调整。
25000个帖子可以很容易地解释你的8.6g
根据Amir评论进行更新:
不是100%肯定但是看一下tour pmap日志,你可能在glibc
中遇到了竞技场分配器的问题查看所有64Mb分配
检查您的glibc版本是否&gt; 2.10
尝试使用环境变量MALLOC_ARENA_MAX = 2设置运行程序。您可以使用实际值。