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An Serviceability-Agent based tool to see stats of NIO direct memory, as an alternative on JDK6 without JMX support for direct memory monitoring. Only works on JDK6; to work on JDK7 will need some tweaking because static variables are moved to Java mirror
$ java -version
java version "1.6.0_30"
Java(TM) SE Runtime Environment (build 1.6.0_30-b12)
Java HotSpot(TM) 64-Bit Server VM (build 20.5-b03, mixed mode)
$ javac -classpath $JAVA_HOME/lib/sa-jdi.jar DirectMemorySize.java
$ jps
18486 GroovyStarter
23135 Jps
$ java -classpath .:$JAVA_HOME/lib/sa-jdi.jar DirectMemorySize `pgrep java`
Attaching to process ID 18486, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 20.5-b03
NIO direct memory: (in bytes)
reserved size = 0.000000 MB (0 bytes)
max size = 4069.000000 MB (4266655744 bytes)
[sajia@211 temp]$ java -cp .:$JAVA_HOME/lib/sa-jdi.jar DirectMemorySize
Usage: java directMemorySize [option] <pid>
(to connect to a live java process)
or java directMemorySize [option] <executable> <core>
(to connect to a core file)
or java directMemorySize [option] [server_id@]<remote server IP or hostname>
(to connect to a remote debug server)
where option must be one of:
-e to print the actual size malloc'd
-v to print verbose info of every live DirectByteBuffer allocated from Java
-h | -help to print this help message
[sajia@211 temp]$ java -cp .:$JAVA_HOME/lib/sa-jdi.jar DirectMemorySize `pgrep -u sajia java`
Attaching to process ID 7381, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 20.5-b03
NIO direct memory: (in bytes)
reserved size = 0.000003 MB (3 bytes)
max size = 7152.000000 MB (7499415552 bytes)
[sajia@211 temp]$ java -cp .:$JAVA_HOME/lib/sa-jdi.jar DirectMemorySize -e `pgrep -u sajia java`
Attaching to process ID 7381, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 20.5-b03
NIO direct memory: (in bytes)
reserved size = 0.000003 MB (3 bytes)
max size = 7152.000000 MB (7499415552 bytes)
Finding object size using Printezis bits and skipping over...
Finding object size using Printezis bits and skipping over...
NIO direct memory malloc'd size: 0.007815 MB (8195 bytes)
[sajia@211 temp]$ time java -cp .:$JAVA_HOME/lib/sa-jdi.jar DirectMemorySize `pgrep -u sajia java`
Attaching to process ID 7381, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 20.5-b03
NIO direct memory: (in bytes)
reserved size = 0.000003 MB (3 bytes)
max size = 7152.000000 MB (7499415552 bytes)
real 0m0.401s
user 0m0.503s
sys 0m0.057s
[sajia@211 temp]$ time java -cp .:$JAVA_HOME/lib/sa-jdi.jar DirectMemorySize -e `pgrep -u sajia java`
Attaching to process ID 7381, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 20.5-b03
NIO direct memory: (in bytes)
reserved size = 0.000003 MB (3 bytes)
max size = 7152.000000 MB (7499415552 bytes)
Finding object size using Printezis bits and skipping over...
Finding object size using Printezis bits and skipping over...
NIO direct memory malloc'd size: 0.007815 MB (8195 bytes)
real 0m4.822s
user 0m2.095s
sys 0m3.216s
[sajia@211 temp]$ time java -cp .:$JAVA_HOME/lib/sa-jdi.jar DirectMemorySize -e -v `pgrep -u sajia java`
Attaching to process ID 7381, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 20.5-b03
NIO direct memory: (in bytes)
reserved size = 0.000003 MB (3 bytes)
max size = 7152.000000 MB (7499415552 bytes)
Currently allocated direct buffers:
0x00002aaab021df10: capacity = 0.000001 MB (1 bytes), mallocSize = 0.003907 MB (4097 bytes)
0x00002aaab0843310: capacity = 0.000002 MB (2 bytes), mallocSize = 0.003908 MB (4098 bytes)
Finding object size using Printezis bits and skipping over...
Finding object size using Printezis bits and skipping over...
NIO direct memory malloc'd size: 0.007815 MB (8195 bytes)
real 0m5.097s
user 0m2.164s
sys 0m3.426s
[sajia@211 temp]$
[sajia@xxx164 gist]$ sudo -u admin java -cp .:$JAVA_HOME/lib/sa-jdi.jar DirectMemorySize -e `pgrep -u admin java` | grep -v 'Finding object'
Attaching to process ID 2499, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 20.0-b12-internal
NIO direct memory: (in bytes)
reserved size = 907.541405 MB (951626136 bytes)
max size = 3925.375000 MB (4116054016 bytes)
NIO direct memory malloc'd size: 910.697655 MB (954935704 bytes)
import java.io.*;
import java.util.*;
import sun.jvm.hotspot.memory.*;
import sun.jvm.hotspot.oops.*;
import sun.jvm.hotspot.debugger.*;
import sun.jvm.hotspot.runtime.*;
import sun.jvm.hotspot.tools.*;
import sun.jvm.hotspot.utilities.*;
public class DirectMemorySize extends Tool {
private boolean exactMallocMode;
private boolean verbose;
public DirectMemorySize(boolean exactMallocMode, boolean verbose) {
this.exactMallocMode = exactMallocMode;
this.verbose = verbose;
}
public void run() {
// Ready to go with the database...
try {
long reservedMemory = getStaticLongFieldValue("java.nio.Bits", "reservedMemory");
long directMemory = getStaticLongFieldValue("sun.misc.VM", "directMemory");
System.out.println("NIO direct memory: (in bytes)");
System.out.printf(" reserved size = %f MB (%d bytes)\n", toM(reservedMemory), reservedMemory);
System.out.printf(" max size = %f MB (%d bytes)\n", toM(directMemory), directMemory);
if (verbose) {
System.out.println("Currently allocated direct buffers:");
}
if (exactMallocMode || verbose) {
final long pageSize = getStaticIntFieldValue("java.nio.Bits", "pageSize");
ObjectHeap heap = VM.getVM().getObjectHeap();
InstanceKlass deallocatorKlass =
SystemDictionaryHelper.findInstanceKlass("java.nio.DirectByteBuffer$Deallocator");
final LongField addressField = (LongField) deallocatorKlass.findField("address", "J");
final IntField capacityField = (IntField) deallocatorKlass.findField("capacity", "I");
final int[] countHolder = new int[1];
heap.iterateObjectsOfKlass(new DefaultHeapVisitor() {
public boolean doObj(Oop oop) {
long address = addressField.getValue(oop);
if (address == 0) return false; // this deallocator has already been run
long capacity = capacityField.getValue(oop);
long mallocSize = capacity + pageSize;
countHolder[0]++;
if (verbose) {
System.out.printf(" 0x%016x: capacity = %f MB (%d bytes),"
+ " mallocSize = %f MB (%d bytes)\n",
address, toM(capacity), capacity,
toM(mallocSize), mallocSize);
}
return false;
}
}, deallocatorKlass, false);
if (exactMallocMode) {
long totalMallocSize = reservedMemory + pageSize * countHolder[0];
System.out.printf("NIO direct memory malloc'd size: %f MB (%d bytes)\n",
toM(totalMallocSize), totalMallocSize);
}
}
} catch (AddressException e) {
System.err.println("Error accessing address 0x"
+ Long.toHexString(e.getAddress()));
e.printStackTrace();
}
}
public static long getStaticLongFieldValue(String className, String fieldName) {
InstanceKlass klass = SystemDictionaryHelper.findInstanceKlass(className);
LongField field = (LongField) klass.findField(fieldName, "J");
return field.getValue(klass); // on JDK7 use: field.getValue(klass.getJavaMirror());
}
public static int getStaticIntFieldValue(String className, String fieldName) {
InstanceKlass klass = SystemDictionaryHelper.findInstanceKlass(className);
IntField field = (IntField) klass.findField(fieldName, "I");
return field.getValue(klass); // on JDK7 use: field.getValue(klass.getJavaMirror());
}
public static double toM(long value) {
return value / (1024 * 1024.0);
}
public String getName() {
return "directMemorySize";
}
protected void printFlagsUsage() {
System.out.println(" -e\tto print the actual size malloc'd");
System.out.println(" -v\tto print verbose info of every live DirectByteBuffer allocated from Java");
super.printFlagsUsage();
}
public static void main(String[] args) {
boolean exactMallocMode = false;
boolean verbose = false;
// argument processing logic copied from sun.jvm.hotspot.tools.JStack
int used = 0;
for (String arg : args) {
if ("-e".equals(arg)) {
exactMallocMode = true;
used++;
} else if ("-v".equals(arg)) {
verbose = true;
used++;
}
}
if (used != 0) {
args = Arrays.copyOfRange(args, used, args.length);
}
DirectMemorySize tool = new DirectMemorySize(exactMallocMode, verbose);
tool.start(args);
tool.stop();
}
}

Also works on core dumps, in the form of:

java -cp .:$JAVA_HOME/lib/sa-jdi.jar DirectMemorySize $JAVA_HOME/bin/java core.xxx
@asafm

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asafm commented Aug 1, 2013

irectMemorySize.java:3: package sun.jvm.hotspot.memory does not exist
import sun.jvm.hotspot.memory.*;
^

Couldn't find this package from some reason. Running on Mac OSX

@caoxudong

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caoxudong commented Aug 7, 2013

@asafm

Package "sun.jvm.hotspot.memory.*" is in the $JAVA_HOME/lib/sa-jdi.jar. Did you add this jar to CLASSPATH?

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fuyou001 commented May 23, 2014

收藏了

@JinhouLiu

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JinhouLiu commented Oct 25, 2014

学习

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allwmh commented Oct 28, 2014

HI 我执行完一次之后。kill -9 DirectMemorySize 的运行进城后,想再次使用就一直连接不上去 。这是为什么呢?

@yikebocai

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yikebocai commented Nov 14, 2014

使用-e-v参数时只显示和不加参数时同样的信息,上面例子上给出的额外信息一直长时间无法显示,是什么原因?

[root@cass047202 ~]# java -classpath .:/usr/install/java/lib/sa-jdi.jar DirectMemorySize -e 2904
Attaching to process ID 2904, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.51-b03
NIO direct memory: (in bytes)
  reserved size = 32686.010643 MB (34273766296 bytes)
  max size      = 27566.686493 MB (28905765856 bytes)

使用环境 CentOS 6.5 64bit,物理内存32G,Jdk7,Xmx8G

还有一个问题,按你这篇文章http://hllvm.group.iteye.com/group/topic/27945 提到的,如果参数 -XX:MaxDirectMemorySize没有设置,默认应该是约等了-Xmx8g这个值,为何这里显示是将近27G?

@simmel

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simmel commented Jan 15, 2015

Any love to port this to JDK8?

@reza987

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reza987 commented Dec 19, 2017

21124143_1044357149040746_2070796490_n
55666

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reza987 commented Dec 19, 2017

he is addicted for yaba for long time he always motivated new one comer.

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ydx2008 commented Mar 5, 2018

can it works on java8?

@Rayn-liuwei

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Rayn-liuwei commented Mar 8, 2018

tool.run(args) modify to tool.execute(args);

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