Unless you have real memory requirements, one tomcat instance is
better, at least in terms of maintenance. There is no real advantage
in multi-instancing.
But the limit for max memory you can effectively use in your java
program on a 32bit linux, i assume you use (same for windows),
lies far
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Leon,
Leon Rosenberg wrote:
But the limit for max memory you can effectively use in your java
program on a 32bit linux, i assume you use (same for windows),
lies far below 2Gb.
I've been trying to find the real nature of this memory limit. I
En l'instant précis du 14/03/07 14:31, Christopher Schultz s'exprimait
en ces termes:
Leon,
Leon Rosenberg wrote:
But the limit for max memory you can effectively use in your java
program on a 32bit linux, i assume you use (same for windows),
lies far below 2Gb.
I've been trying to
From: Christopher Schultz [mailto:[EMAIL PROTECTED]
Subject: [OT]Re: Is better one or more Tomcat instances per machine
The below applies only to 32-bit systems, of course.
Some claim that 32-bit OSs can't use more than 4GB RAM
Lots of people seem to confuse virtual space with real memory
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On 14/03/2007, at 2:31 PM, Christopher Schultz wrote:
The reading I've done so far on this subject leads me to believe that
most people don't know what they heck they're talking about. Some
claim
that 32-bit OSs can't use more than 4GB RAM (they
From: Leon Rosenberg [mailto:[EMAIL PROTECTED]
There is no real advantage in multi-instancing.
A minor advantage is that if you allocate one webapp per container, if
one webapp fails it only takes down its own container. Well-coded
webapps should never cause this - and, of course, we all
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On 14/03/2007, at 3:11 PM, David Delbecq wrote:
This has changed. An new architecture was brought in CPU (at
pentium II
time?) that allowed OS to do a 4G/4G mapping in 32 bits mode. Since
you
don't access kernel space from user mode directly,
From: Andrew Miehs [mailto:[EMAIL PROTECTED]
32bit OSes can not use more than 4GB RAM. What you are probably
referring
to is PAE, and there the kernel splits the 'extra' memory into
chunks, and
can give each process part of this chunk - a single process however,
under
linux can not
On 14/03/2007, at 3:17 PM, Peter Crowther wrote:
From: Leon Rosenberg [mailto:[EMAIL PROTECTED]
There is no real advantage in multi-instancing.
A minor advantage is that if you allocate one webapp per container, if
one webapp fails it only takes down its own container. Well-coded
webapps
On 14/03/2007, at 3:21 PM, Peter Crowther wrote:
Let's be clear about the distinction between OS and process managed
by OS:
- The OS as a whole can manage 4 Gbytes of physical memory using
PAE;
- On some OSs (Linux, perhaps?), a user process cannot be allocated
4
Gbytes of RAM;
Sorry,
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David,
David Delbecq wrote:
32 bits architecture, a memory pointer is 32 bits and thus can only
address memory ranges between 0 to 2^32, that makes 4G
back in kernel 2.4 time
Pointers didn't get bigger in 2.6, so the 4GB process limit is still
From: Andrew Miehs [mailto:[EMAIL PROTECTED]
Subject: Re: [OT]Re: Is better one or more Tomcat instances
per machine
The user space is the amount of RAM you as a process can
allocate for this single process.
No - RAM has nothing to do with the split. Process memory is the amount
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Chuck,
I knew you'd come through. It's always nice to have a VM hacker around
for questions like this.
Caldarale, Charles R wrote:
that they have 2GB/2GB kernel and process memory boundaries
Windows certainly does have such a boundary (although
From: Christopher Schultz [mailto:[EMAIL PROTECTED]
Subject: Re: [OT]Re: Is better one or more Tomcat instances
per machine
I don't think this has anything to do with hardware.
It does. To quote from the IA32 architecture spec:
Starting with the Pentium Pro processor, the IA-32
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Andrew,
Andrew Miehs wrote:
32bit OSes can not use more than 4GB RAM.
??!
A process on a 32-bit OS can't use more than 4GB of RAM, but the OS
certainly can.
2GB/2GB kernel and process memory boundaries (they don't, except that I
think MS
of ram, I will test it
as soon as I get some time.
Andrew Pliszka
Caldarale, Charles R wrote:
From: Andrew Miehs [mailto:[EMAIL PROTECTED]
Subject: Re: [OT]Re: Is better one or more Tomcat instances
per machine
The user space is the amount of RAM you as a process can
allocate
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On 14/03/2007, at 3:52 PM, Caldarale, Charles R wrote:
The user space is the amount of RAM you as a process can
allocate for this single process.
No - RAM has nothing to do with the split. Process memory is the
amount
of virtual space
From: Christopher Schultz [mailto:[EMAIL PROTECTED]
Subject: Re: [OT]Re: Is better one or more Tomcat instances
per machine
Hmm perhaps I have a virtual memory limit. I have 1GB
of physical RAM. While allocating a 3GB heap is pretty
stupid for me, I still ought to be able to do
From: Andrew Miehs [mailto:[EMAIL PROTECTED]
Subject: Re: [OT]Re: Is better one or more Tomcat instances
per machine
Your kernel, and the things which are doing your process
switching need somewhere to run - if you switch them out
of your 4GB of virtual address space, how are they ever
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Chuck,
Caldarale, Charles R wrote:
From: Christopher Schultz [mailto:[EMAIL PROTECTED]
Hmm perhaps I have a virtual memory limit. I have 1GB
of physical RAM. While allocating a 3GB heap is pretty
stupid for me, I still ought to be able to
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Chuck,
Caldarale, Charles R wrote:
From: Christopher Schultz [mailto:[EMAIL PROTECTED]
Subject: Re: [OT]Re: Is better one or more Tomcat instances
per machine
I don't think this has anything to do with hardware.
It does. To quote from
Heh - ask Murphy about that :)
just spawn a thread set priority high and loop forever.
At 10:23 3/14/2007, you wrote:
On 14/03/2007, at 3:17 PM, Peter Crowther wrote:
From: Leon Rosenberg [mailto:[EMAIL PROTECTED]
There is no real advantage in multi-instancing.
A minor advantage is that if
From: Christopher Schultz [mailto:[EMAIL PROTECTED]
Subject: Re: [OT]Re: Is better one or more Tomcat instances
per machine
I guess that Linux not only does optimistic malloc, but also
optimistic calloc as well. I had hoped that zeroing-out the
memory would count as a write
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Chuck,
Caldarale, Charles R wrote:
From: Christopher Schultz [mailto:[EMAIL PROTECTED]
Subject: Re: [OT]Re: Is better one or more Tomcat instances
per machine
I guess that Linux not only does optimistic malloc, but also
optimistic calloc
From: Christopher Schultz [mailto:[EMAIL PROTECTED]
Subject: Re: [OT]Re: Is better one or more Tomcat instances
per machine
The fact remains that you can't allocate a VM heap bigger than around
1750MB on my 32-bit, 2.6 Linux kernel. Why not?
You have to wait for a full moon...
- Chuck
| From: Christopher Schultz [mailto:[EMAIL PROTECTED]
| Sent: Wednesday, 14 March, 2007 10:37
|
| The fact remains that you can't allocate a VM heap bigger than around
| 1750MB on my 32-bit, 2.6 Linux kernel. Why not?
If, as you stated earlier, you only have 1G of physical and 1G of virtual
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Tracy,
Nelson, Tracy M. wrote:
| From: Christopher Schultz [mailto:[EMAIL PROTECTED]
| Sent: Wednesday, 14 March, 2007 10:37
|
| The fact remains that you can't allocate a VM heap bigger than around
| 1750MB on my 32-bit, 2.6 Linux kernel. Why
From: Christopher Schultz [mailto:[EMAIL PROTECTED]
Subject: Re: [OT]Re: Is better one or more Tomcat instances
per machine
For instance, java -Xmx512M -Xms512M -version bombs on this little
box, even though the heap is pretty much never used.
The JVM requests all 512 MB at startup
| From: Christopher Schultz [mailto:[EMAIL PROTECTED]
| Sent: Wednesday, 14 March, 2007 12:05
|
| Perhaps, but the JVM actually refuses to start right away. In my eat
| all my memory tests, I was able to eat around 1.6GB before I brought my
| machine to a crawl. It took more than a minute for my
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Tracy,
Nelson, Tracy M. wrote:
I imagine that when the JVM calls [cm]alloc, one of the first things alloc()
does is call sbrk() to expand your process' memory space. That'll fail
right away if you don't have enough VM available.
I do not
| From: Christopher Schultz [mailto:[EMAIL PROTECTED]
| Sent: Wednesday, 14 March, 2007 15:02
|
| In my tests on the larger machine, the JVM kindly tells me that it can't
| give me that much memory, rather than crashing and burning as I would
| expect after being tricked by the OS.
Perhaps the
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