java memory profiling tools

In the previous article. We have listed several conclusions about calculating the size of Java objects and the use of Jol tools, and the source code of the Jol tool is interesting to look at. Now we use the Sun.misc.Unsafe in the JDK to calculate the offset address of the next field, a validation of the conclusions in the previous article, and a comparison with the Jol output results. How to get the Sun.mis

1. Self-jconsole tools.(1) Assume that you start from the command line so that the JDK is on PATH and executes Jconsole.(2) Suppose you start from the GUI shell, find the JDK installation path, open the Bin directory, and double-click jconsole .(3) When the analysis tool pops up (depending on the Java version number being executed and the number of Java programs

When there is a heapdumponoutofmemoryerror error, we need to analyze the reason, the following program is to simulate this error and export the dump file, so that you analyzeGctest.java PackageGC; Public classGctest {Private Static Final int_1mb= 1024 * 1024;//approx. 1m Public Static voidMain (string[] args) {//a total of about 8m, heap size set not more than 8388608B that is 8.388608m memory overflow, but need an integer, less than 8M

Solution: There is a dx.bat in android->sdk->build-tools-android-versionDx.bat--dexThe Dx.bat script for the command has such a codeREM by default, give DX a max heap size of 1 gig and a stack size of 1meg.rem This can is overridden by using "-jxmx ..." a nd "-JXSS ..." Options Below.set defaultxmx=-xmx1024mset defaultxss=-xss1mSet defaultxmx=-xmx1024mThe reason is that the xmx set here is 1024M, when compiling the package apk, the

It is said that once the SQL query returns too much data, it can cause server memory overflow.However, I now encounter the situation is that call a PostgreSQL stored procedure, very complex, then there are many raise notice such debugging statements, if happen to have a dead loop, then, these raise notice message will be sent to the server, It will eventually cause a server memory overflow.(specifically, th

If you use a file system such as Luncene or Hadoop, there are a large number of index files to be distributed, you can use ready-made distribution tools, or you can write your own program for quick file copy;Use NIO make quick copies of filesPackage com.daily;Import Java.io.File;Import Java.io.FileInputStream;Import Java.io.FileOutputStream;Import java.io.IOException;Import Java.nio.channels.FileChannel;/***nio fast file copy, maxcount=128m, copy 351M

= Connector.getmbeanserverconnection (); ObjectName ObjectName =NewObjectName ("Java.nio:type=bufferpool,name=direct") ; Mbeaninfo mbinfo = Mbsc.getmbeaninfo (objectName); for(Mbeanattributeinfo i:mbinfo.getattributes ()) {System.out. println (I.getname () +":"+ Mbsc.getattribute (ObjectName, I.getname ()));}Second, using unsafe reflection calls directly requested out of the heap memoryJava is not available, requires tools like Gperftools to view, ne

resultsRs.close ();}catch (Exception e) {E.printstacktrace ();}rs= null;}if (st! = null) {try{ // Close the statement object that is responsible for executing the SQL commandSt.close ();}catch (Exception e) {E.printstacktrace ();}}IF (conn! = null) {try{ // Returning the connection connection object to the database connection poolConn.close ();}catch (Exception e) {E.printstacktrace ();}}}publicstatic void Main (string[] args) {Connectioncon = null;PREPAREDSTATEMENTST = null;Resultsetrs = null;