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From "Jeff Kilbride" <j...@kilbride.com>
Subject Re: ** JVM and Processes
Date Fri, 01 Jun 2001 18:57:03 GMT
Hi Adam,

No, the garbage collector runs as a low priority background process and, on
a lightly loaded server, may never get called because the server's not using
enough resources to warrant it. I really wouldn't worry about it too much
and I would definitely avoid killing threads individually, especially since
you're now utilizing a Pool connector. (you don't want to kill threads that
are marked as available in the pool...) The min_spare_threads and
max_spare_threads settings are supposed to take care of cleaning up any
"extra" unused threads that are laying around.

I think the best benefit you could do yourself would be to upgrade your 3.1
version of Tomcat to the newly released 3.2.2 final to take advantage of
upgrades and bug fixes.

Thanks,
--jeff

----- Original Message -----
From: <myatt83@potsdam.edu>
To: <tomcat-user@jakarta.apache.org>
Sent: Friday, June 01, 2001 11:03 AM
Subject: Re: ** JVM and Processes


> Jeff,
>
> Thanks a bunch. Your answer appears to be the best so far. I have
> implemented the PoolTCPConnector in the server xml file and it appears to
> be limiting the number of threads as it should. However, something that
has
> been happening (even before switching to PoolTCPConnector) is that when
> running multiple java servlets the threads stay alive long after they
> should have died or been garbage collected. Even after a long wait, the
> only way (apparently) to get rid of them is to go through and kill them
one
> at a time. Is there a setting somewhere that is telling the java threads
to
> stay alive indefinitely?
>
> Thanks for your help,
>  - Adam
>
>
> At 10:34 AM 6/1/2001 -0700, you wrote:
> >When Java first came to the Linux platform (via the Blackdown port),
> >green-threads were the only option. Native threads took a little longer
to
> >implement, but are a much better option for the reasons listed in the
> >previous message. So, I would recommend avoiding green-threads unless you
> >have a specific reason for using them.
> >
> >A lot of people freak out when they see the number of "processes" being
> >reported by ps or top, without realizing that these are merely threads
and
> >not full-blown processes. If you have a lightly loaded Tomcat, you can
tune
> >down the number of threads being spawned by using the max_threads,
> >max_spare_threads, and min_spare_threads parameters of the
PoolTCPConnector
> >in your server.xml file. For an example of this, take a look at the
tomcat
> >user's guide:
> >
> >http://jakarta.apache.org/tomcat/tomcat-3.2-doc/index.html
> >
> >Do a "find" in your web browser for "max_threads". I use this to limit
the
> >number of ajp12 threads and maximize ajp13 threads -- because I'm using
> >ajp13 for my servlets and ajp12 only for startup/shutdown of Tomcat.
> >
> >Conversely, if you have a heavily loaded Tomcat, you should use these
> >parameters to increase performance.
> >
> >Thanks,
> >--jeff
> >
> >----- Original Message -----
> >From: "Michael Jennings" <southgate.software@home.com>
> >To: <tomcat-user@jakarta.apache.org>
> >Sent: Friday, June 01, 2001 9:32 AM
> >Subject: Re: ** JVM and Processes
> >
> >
> >RE: ** JVM and ProcessesMy understanding of green vs. native threads is
as
> >follows:
> >With native threads, an actual system thread is created when a Java
thread
> >is created.
> >On linux a system thread takes the form of another process, but one that
> >shares memory
> >etc. with another process. This is why if you create a program that
> >allocates 100 megs of memory,
> >then spins off 10 threads, it looks like 10 processes each taking up 100
> >megs of memory, when in
> >fact the amount of memory is 100 megs + 10*overhead for each thread (not
> >much more than 100 megs).
> >
> >On WIN32 systems, threads do not show up as separate processes, they are
> >separate threads of execution
> >inside the same process (essentially the same as the Linux implementation
> >with differences too subtle to care about)
> >
> >Green threads on the other hand use timers, signals, setjmp etc. voodoo
to
> >"simulate" threads within one process.
> >Essentially taking over the scheduling from the kernel.
> >
> >I believe the command-line option for green threads is simply "-green" as
in
> >java -green MyThreaddedApp
> >
> >If you have a multi-cpu system, green threads will only take advantage of
> >one cpu, whereas native threads
> >will use all the cpus on your system (that's the theory anyway)
> >
> >I've heard of problems with blocking I/O with green threads, but have no
> >first hand knowledge.
> >
> >Hope this helps.
> >-Mike Jennings
> >
> >  ----- Original Message -----
> >  From: BARRAUD Valérie
> >  To: 'tomcat-user@jakarta.apache.org'
> >  Sent: Friday, June 01, 2001 9:01 AM
> >  Subject: RE: ** JVM and Processes
> >
> >
> >
> >
> >  http://java.sun.com/products/jdk/1.1/packs/native-threads/README
> >
> >    -----Message d'origine-----
> >    De:     myatt83@potsdam.edu [SMTP:myatt83@potsdam.edu]
> >    Date:   vendredi 1 juin 2001 17:46
> >    À:      tomcat-user@jakarta.apache.org
> >    Objet:  RE: ** JVM and Processes
> >
> >    Randy,
> >
> >    Thanks for the advice. Could you be a little more specific, though,
> >about
> >    how to use green threads instead of native threads and possibly
> >differences
> >    between the two? Thanks.
> >
> >     - Adam
> >
> >
> >
> >    At 10:59 AM 6/1/2001 -0400, you wrote:
> >    >
> >    >       Don't use ps - these are actually threads.  ps is showing
them
> >as
> >    >processes because that is what it does.  If you use green thread (as
> >opposed
> >    >to the native threads you are using now), the display will go away,
but
> >you
> >    >will experience a slowdown (how much depends on your operating
system
> >and
> >    >other activity on the system).
> >    >
> >    >       Randy
> >    >
> >    >
> >    >> -----Original Message-----
> >    >> From: myatt83@potsdam.edu [mailto:myatt83@potsdam.edu]
> >    >> Sent: Friday, June 01, 2001 10:37 AM
> >    >> To: tomcat-user@jakarta.apache.org
> >    >> Subject: ** JVM and Processes
> >    >>
> >    >>
> >    >> Hi,
> >    >>
> >    >> For a particular web server we are running with Tomcat 3.1,
> >    >> we are having
> >    >> an issue with the java servlets that are running. What appears to
be
> >    >> happening is that each time a servlet is called from the web
> >    >> site, a new
> >    >> process is created to run the java program. When I view
> >    >> processes with "ps
> >    >> ax", I see dozens of instances of:
> >    >> /usr/java/jdk1.3/bin/i386/native_threads/java
> >    >>
> >    >> It was briefly stated in Java Servlet Programming by Hunter &
> >    >> Crawford, (c)
> >    >> Oreilly that 'most servlet containers execute all servlets in
> >    >> a single JVM
> >    >> ... the exception being high-end containers that support
> >    >> execution across
> >    >> multiple backend servers...'
> >    >>
> >    >> We are only using 1 web server with an average weekly load of
> >    >> a couple of
> >    >> hundred visitors.
> >    >>
> >    >> Any ideas as to why we would be seeing so many identical
> >    >> processes and if
> >    >> so, how to modify that?
> >    >>
> >    >> Thanks in advance.
> >    >>
> >    >>   -Adam
> >    >>
> >    >>
> >    >
> >    >
> >
> >
> >
> >
> >
>


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