Re: Java 5 threads in linux

From:

Lew <lew@nospam.lewscanon.com>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 20 Apr 2007 22:22:48 -0400

Message-ID:

<IMGdnTybAdnk6LTbnZ2dnUVZ_sapnZ2d@comcast.com>

Sunny wrote:

I am relatively new in java and know little about the history of JVM.
In a previous document SUN has provided the following information for
java version "1.3.0" in Linux platform (from
http://java.sun.com/developer/technicalArticles/Programming/linux/ ):

Java 1.3 is obsolete.

Nothing about the Java 1.3 JVM can be used to draw conclusions about the
current Sun implementation, much less anyone else's, wrt thread-to-process
mapping.

As I have started with the version 1.5, don't know if the native
threads support is still threre in this version.

"Still" there? The point is that Java 1.3 did not have native thread support,
but mapped threads to processes in Linux.

Is there any doc from SUN or, other to describe the threads behaviour in new version of JVM
in Linux platform?

Surely I can use 'ps' command to see if the code line creates
processes. The problem is elsewhere. While I was using the
ExecutorService high level API to manage threads, I got an error which
states "unable to create new native thread". The exact message is
"java.lang.OutOfMemoryError: unable to create new native thread".
Native thread must be linux system threads (may be POSIX). But the
'ps' command is not showing multiple JVM threads.

With what options did you invoke 'ps'?

Either the error message is wrong when JVM is running in Linux system
or, 'ps' command is not showing up the java native threads correctly.

You haven't told us what you regard as "correctly" nor how you ran "ps", nor
precisely what the output was, nor precisely how it differed from what you
want. That information would be useful for anyone wishing to comment on your
situation.

Please share your experience on it.

I tried this on my Linux system:

$ ps -C java -o "pid,lwp,comm"
   PID LWP COMMAND
  4848 4848 java
  5987 5987 java

Then this:

$ ps -C java -Lo "pid,lwp,comm"
   PID LWP COMMAND
  4848 4848 java
  4848 4849 java
  4848 4850 java
  4848 4851 java
  4848 4852 java
  4848 4853 java
  4848 4854 java
  4848 4855 java
  4848 4856 java
  4848 4857 java
  4848 4858 java
  4848 4859 java
  4848 4860 java
  4848 4861 java
  4848 4863 java
  ...

Is this anything like what you experienced?

--
Lew