RE: Does tomcat support multicores

[Baron, Bob (LNG-HBE)]

It works just fine!

My guess would be that the load you're putting on it is single threaded, so 
there's only a single thread executing on the server. You're really only asking 
it to do one thing at a time.

Make sure that you're running multiple concurrent loads.

-Original Message-
From: Christopher Schultz [mailto:[EMAIL PROTECTED] 
Sent: Thursday, February 28, 2008 11:03 AM
To: Tomcat Users List
Subject: Re: Does tomcat support multicores

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James,

James Law wrote:
| Os - WinXP
|
| CPU - Intel Quad Core
|
| Hi I'm running a tomcat server, and would like to know if Tomcat can
| make use of multiple cores? When I max the server out, all 4 cores see
| little usage however the java process never uses more than 25%.

Sounds like you haven't really maxed-out your server. What is your
definition of maxed-out?

| So this makes me believe that Tomcat does not make use of a multicore
| system.

Just like most hardware resource questions in Tomcat, it all comes down
to the JVM + the OS. Tomcat itself neither enables nor disables this
capability. The JVM supports multiple threads. The OS supports threads.
Presumably, the OS is smart enough to allow threads from a single
process to run on any CPU (or core).

| Would I benefit from running more than one instance and setup load
| bearing between the two?

Probably not. I would venture a guess that you are seeing appropriate
resource usage for your load scenario. What does maxed-out mean, and
why do you think you are in that state? Can you see which processor(s)
is(are) running java.exe (or whatever) processes, or are you just
looking at the overall CPU-usage meter and seeing that it shows 25%
total CPU usage? There's also the possibility that your application is
I/O-bound instead of CPU bound, meaning that the CPU is spending most of
the time waiting around for data to move around instead of performing
calculations and whatnot. That wouldn't be a surprise given that network
transfer speeds are relatively slow compared to bus speeds and the rate
at which your CPU(s) can process information.

- -chris
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RE: is there a limit to JAVA Heap size ?

[Baron, Bob (LNG-HBE)]

First of all, this is a JRE issue, not Tomcat!

Depending on your Operating system (Windows, *nix, etc.), whether it's a
32 or 64 bit version, and what JRE you're using, the limit is different.
You can get pretty good info from you JRE vendor about how it uses
memory - Sun has several good articles on it - especially how they
relate to Garbage Collection.

Under 32 bit Windows, the JRE process is limited to 2 GB of total memory
- including the memory that the JRE needs other than the heap controlled
by the -Xmx setting. 

The practical limit is about 1250 MB for 32-bit Windows with a 1.5 or
1.6 Sun JRE. The limit for 64-bit Windows is insanely high - I hope to
not ever reach it in my lifetime!

Whatever your environment, a little trial-and-error can be used. Simply
run something like 'java -Xmx2048M foo'. This is trying to set it to
2GB. Change the numeric value up and down to find out what your limit
is. The Sun JRE gives an error about allocating the memory before
worrying about not finding foo.

-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] 
Sent: Monday, November 26, 2007 12:12 PM
To: Tomcat Users List
Subject: Re: is there a limit to JAVA Heap size ?

Microsoft allows 3GB capability for User Process Address Space
http://www.microsoft.com/technet/sysinternals/information/bootini.mspx

Anyone else?
M--
- Original Message - 
Wrom: UZXUWLSZLKBRNVWWCUFPEGAUTFJMVRESKPNKMBIPB
To: Tomcat Users List users@tomcat.apache.org
Sent: Monday, November 26, 2007 12:08 PM
Subject: Re: is there a limit to JAVA Heap size ?


 Jean,
 
 I am not a Tomcat Expert, though I know you can set this value to a
 higher number. I have set once to 1GB.
 
 Perhaps the gurus on the forum would answer it clearly to you.
 
 HTH
 
 Bruno
 
 On Nov 26, 2007 3:06 PM, Jean-Pierre Astier [EMAIL PROTECTED]
wrote:
  Hello,
 
  An other little question !!!
 
  Is there a limit to the java heap size var environment ?
 
  There is 3 GB off RAM on my server.
 
  I've set JAVA_OPTS to -Xms512m -Xmx512m in catalina.sh.
 
  Can I increase more than this value ?
 
  Thanks
 
 
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