Java overhead Post: 302487182

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Top Forums Web Development Java overhead Post 302487182 by DGPickett on Tuesday 11th of January 2011 03:56:56 PM

01-11-2011

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Well, you can control JAVA behaviors with -X and other command line arguments, for instance to set the heap size -Xmx very high and to specify how much GC cost you want. GC is forced when the heap fills, and the heap is VM, disk is cheap, newer JAVA has nice GC, parallel and heuristic. These options also can turn on parrallel buffered I/O, resulting in fewer real reads and writes, faster with lower overhead, no code but one option.

Using a "Server" grade platform and server mode java means the code is more optimized.

Using 64 bit mode unnecessarily may add some overhead.

RAM is VM, so "RAM in use" is a useless concept. If a program using 20M of RAM exits, there is 20M free until there are 20M new page faults -- so what? Do you have too much paging?

CPU use is pretty much dependent on economical programming, finesse and real load. Finding out what code is the CPU hog is a big industry, easier in C/C++ than JAVA, as a short truss/tusc/strace of a JAVA process does not tell you much. Creation and destruction of complex objects frequently is a great cost, in JAVA or C++, and worse in JAVA since it forces more GC. Sometimes jobs running continuously can be run at intervals and in sequence, not in parallel, so they do not start the machine thrashing or peak the CPU usage.

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LEARN ABOUT DEBIAN

freemind

FREEMIND(1)						      General Commands Manual						       FREEMIND(1)

NAME

       freemind -- A Java program for creating and viewing mindmaps.

SYNOPSIS

       freemind [no_options]

DESCRIPTION

       This manual page documents briefly the freemind command.

       This  manual  page was written for the Debian distribution because the original program does not have a manual page.  Instead, it has docu-
       mentation as a mindmap (see Help menu in FreeMind).

       freemind is a program that allows to create and view so-called mindmaps, as well as export them to HTML or  different  image  formats.	It
       also has a plugin concept to extend its functionality.

OPTIONS

       This program does not have any option. Just start it!

ENVIRONMENT VARIABLES

       DEBUG	 If   this  environment  variable  is set, freemind gives more information on how it finds its different elements, as well as some
		 other information.

       JAVACMD	 Default value for the java virtual machine (the java command).

       JAVA_BINDIR
		 If $JAVACMD is not set, the java virtual machine is searched under $JAVA_BINDIR/java.

       JAVA_HOME If $JAVACMD and $JAVA_BINDIR are not set, the java virtual machine is searched under $JAVA_HOME/bin/java.

       PATH	 If all $JAVA... environment variables fail, the java virtual machine command (java) is searched in the $PATH (with which).

       CLASSPATH	ADD_JARS
		 The $CLASSPATH variable also lets one specify additional jars, which is good, if you want to add a new Look&Feel jar  (the  motif
		 one is so ugly...). Alternatively, the content of $ADD_JARS will be prepended to $CLASSPATH.

       FREEMIND_BASE_DIR
		 Directory where FreeMind searches for its plugins and libraries

FILES

       /etc/freemind/freemindrc        ~/.freemind/freemindrc
		 freemind  tries to read its environment variables from /etc/freemind/freemindrc and ~/.freemind/freemindrc, so that specific set-
		 tings are possible at machine and user level.

       /usr/bin/java
		 If all searches through environment variables fail, the java virtual machine is expected to be /usr/bin/java;	if  not,  freemind
		 exits with an error.

SEE ALSO

       The  online  documentation under http://freemind.sf.net/, especially the Linux related one under the Wiki page link http://freemind.source-
       forge.net/wiki/index.php/FreeMind_on_Linux.

AUTHOR

       This manual page was written by Eric Lavarde deb@zorglub.s.bawue.de for the Debian system (but may  be  used  by  others).   Permission	is
       granted to copy, distribute and/or modify this document under the terms of the GNU General Public License, Version 2 any later version pub-
       lished by the Free Software Foundation.

       On Debian systems, the complete text of the GNU General Public License can be found in /usr/share/common-licenses/GPL.

																       FREEMIND(1)