flink版本: flink-1.11.2
代码位置: org.apache.flink.runtime.util.EnvironmentInformation#getMaxJvmHeapMemory
如果设置了-Xmx参数，就返回这个参数，如果没设置就返回机器物理内存的1/4. 这里主要看各个机器内存的获取方法。
java
/**
* The maximum JVM heap size, in bytes.
*
* <p>This method uses the <i>-Xmx</i> value of the JVM, if set. If not set, it returns (as
* a heuristic) 1/4th of the physical memory size.
*
* @return The maximum JVM heap size, in bytes.
*/
public static long getMaxJvmHeapMemory() {
final long maxMemory = Runtime.getRuntime().maxMemory();
if(maxMemory != Long.MAX_VALUE) {
// we have the proper max memory
return maxMemory;
} else {
// max JVM heap size is not set - use the heuristic to use 1/4th of the physical memory
final long physicalMemory = Hardware.getSizeOfPhysicalMemory();
if(physicalMemory != -1) {
// got proper value for physical memory
return physicalMemory / 4;
} else {
throw new RuntimeException(
"Could not determine the amount of free memory.\n" + "Please set the maximum memory for the JVM, e.g. -Xmx512M for 512 megabytes.");
}
}
}进入getSizeOfPhysicalMemory()方法，里面有获取各种操作系统物理内存的方法:
java
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.flink.runtime.util;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.lang.management.ManagementFactory;
import java.lang.management.OperatingSystemMXBean;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.flink.util.OperatingSystem;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Convenience class to extract hardware specifics of the computer executing the running JVM.
*/
public class Hardware {
private static final Logger LOG = LoggerFactory.getLogger(Hardware.class);
private static final String LINUX_MEMORY_INFO_PATH = "/proc/meminfo";
private static final Pattern LINUX_MEMORY_REGEX = Pattern.compile("^MemTotal:\\s*(\\d+)\\s+kB$");
// ------------------------------------------------------------------------
/**
* Gets the number of CPU cores (hardware contexts) that the JVM has access to.
*
* @return The number of CPU cores.
*/
public static int getNumberCPUCores() {
// TODO_MA 注释： 获取 Cpu Cores
return Runtime.getRuntime().availableProcessors();
}
/**
* Returns the size of the physical memory in bytes.
*
* @return the size of the physical memory in bytes or {@code -1}, if
* the size could not be determined.
*/
public static long getSizeOfPhysicalMemory() {
// first try if the JVM can directly tell us what the system memory is
// this works only on Oracle JVMs
try {
Class<?> clazz = Class.forName("com.sun.management.OperatingSystemMXBean");
Method method = clazz.getMethod("getTotalPhysicalMemorySize");
OperatingSystemMXBean operatingSystemMXBean = ManagementFactory.getOperatingSystemMXBean();
// someone may install different beans, so we need to check whether the bean
// is in fact the sun management bean
if (clazz.isInstance(operatingSystemMXBean)) {
return (Long) method.invoke(operatingSystemMXBean);
}
}
catch (ClassNotFoundException e) {
// this happens on non-Oracle JVMs, do nothing and use the alternative code paths
}
catch (NoSuchMethodException | IllegalAccessException | InvocationTargetException e) {
LOG.warn("Access to physical memory size: " +
"com.sun.management.OperatingSystemMXBean incompatibly changed.", e);
}
// we now try the OS specific access paths
switch (OperatingSystem.getCurrentOperatingSystem()) {
case LINUX:
return getSizeOfPhysicalMemoryForLinux();
case WINDOWS:
return getSizeOfPhysicalMemoryForWindows();
case MAC_OS:
return getSizeOfPhysicalMemoryForMac();
case FREE_BSD:
return getSizeOfPhysicalMemoryForFreeBSD();
case UNKNOWN:
LOG.error("Cannot determine size of physical memory for unknown operating system");
return -1;
default:
LOG.error("Unrecognized OS: " + OperatingSystem.getCurrentOperatingSystem());
return -1;
}
}
/**
* Returns the size of the physical memory in bytes on a Linux-based
* operating system.
*
* @return the size of the physical memory in bytes or {@code -1}, if
* the size could not be determined
*/
private static long getSizeOfPhysicalMemoryForLinux() {
try (BufferedReader lineReader = new BufferedReader(new FileReader(LINUX_MEMORY_INFO_PATH))) {
String line;
while ((line = lineReader.readLine()) != null) {
Matcher matcher = LINUX_MEMORY_REGEX.matcher(line);
if (matcher.matches()) {
String totalMemory = matcher.group(1);
return Long.parseLong(totalMemory) * 1024L; // Convert from kilobyte to byte
}
}
// expected line did not come
LOG.error("Cannot determine the size of the physical memory for Linux host (using '/proc/meminfo'). " +
"Unexpected format.");
return -1;
}
catch (NumberFormatException e) {
LOG.error("Cannot determine the size of the physical memory for Linux host (using '/proc/meminfo'). " +
"Unexpected format.");
return -1;
}
catch (Throwable t) {
LOG.error("Cannot determine the size of the physical memory for Linux host (using '/proc/meminfo') ", t);
return -1;
}
}
/**
* Returns the size of the physical memory in bytes on a Mac OS-based
* operating system
*
* @return the size of the physical memory in bytes or {@code -1}, if
* the size could not be determined
*/
private static long getSizeOfPhysicalMemoryForMac() {
BufferedReader bi = null;
try {
Process proc = Runtime.getRuntime().exec("sysctl hw.memsize");
bi = new BufferedReader(new InputStreamReader(proc.getInputStream()));
String line;
while ((line = bi.readLine()) != null) {
if (line.startsWith("hw.memsize")) {
long memsize = Long.parseLong(line.split(":")[1].trim());
bi.close();
proc.destroy();
return memsize;
}
}
} catch (Throwable t) {
LOG.error("Cannot determine physical memory of machine for MacOS host", t);
return -1;
} finally {
if (bi != null) {
try {
bi.close();
} catch (IOException ignored) {}
}
}
return -1;
}
/**
* Returns the size of the physical memory in bytes on FreeBSD.
*
* @return the size of the physical memory in bytes or {@code -1}, if
* the size could not be determined
*/
private static long getSizeOfPhysicalMemoryForFreeBSD() {
BufferedReader bi = null;
try {
Process proc = Runtime.getRuntime().exec("sysctl hw.physmem");
bi = new BufferedReader(new InputStreamReader(proc.getInputStream()));
String line;
while ((line = bi.readLine()) != null) {
if (line.startsWith("hw.physmem")) {
long memsize = Long.parseLong(line.split(":")[1].trim());
bi.close();
proc.destroy();
return memsize;
}
}
LOG.error("Cannot determine the size of the physical memory for FreeBSD host " +
"(using 'sysctl hw.physmem').");
return -1;
}
catch (Throwable t) {
LOG.error("Cannot determine the size of the physical memory for FreeBSD host " +
"(using 'sysctl hw.physmem')", t);
return -1;
}
finally {
if (bi != null) {
try {
bi.close();
} catch (IOException ignored) {}
}
}
}
/**
* Returns the size of the physical memory in bytes on Windows.
*
* @return the size of the physical memory in bytes or {@code -1}, if
* the size could not be determined
*/
private static long getSizeOfPhysicalMemoryForWindows() {
BufferedReader bi = null;
try {
Process proc = Runtime.getRuntime().exec("wmic memorychip get capacity");
bi = new BufferedReader(new InputStreamReader(proc.getInputStream()));
String line = bi.readLine();
if (line == null) {
return -1L;
}
if (!line.startsWith("Capacity")) {
return -1L;
}
long sizeOfPhyiscalMemory = 0L;
while ((line = bi.readLine()) != null) {
if (line.isEmpty()) {
continue;
}
line = line.replaceAll(" ", "");
sizeOfPhyiscalMemory += Long.parseLong(line);
}
return sizeOfPhyiscalMemory;
}
catch (Throwable t) {
LOG.error("Cannot determine the size of the physical memory for Windows host " +
"(using 'wmic memorychip')", t);
return -1L;
}
finally {
if (bi != null) {
try {
bi.close();
} catch (Throwable ignored) {}
}
}
}
// --------------------------------------------------------------------------------------------
private Hardware() {}
}另外注意try catch的这种用法:
java
try (BufferedReader lineReader = new BufferedReader(new FileReader(LINUX_MEMORY_INFO_PATH))) {
String line;
while ((line = lineReader.readLine()) != null) {
Matcher matcher = LINUX_MEMORY_REGEX.matcher(line);
if (matcher.matches()) {
String totalMemory = matcher.group(1);
return Long.parseLong(totalMemory) * 1024L; // Convert from kilobyte to byte
}
}
// expected line did not come
LOG.error("Cannot determine the size of the physical memory for Linux host (using '/proc/meminfo'). " +
"Unexpected format.");
return -1;
}
catch (NumberFormatException e) {
LOG.error("Cannot determine the size of the physical memory for Linux host (using '/proc/meminfo'). " +
"Unexpected format.");
return -1;
}