[TriLUG] Memory Monitor on a Redhat system

[Andrew C. Oliver]

This is not true.  JBoss cannot take up more memory than Java is taking 
up (look at RSS in "top").  Java can take up to 4GB including 
HEAP+stack+stuff (probably 3g) on a 32 bit lintel system (max 2 which is 
~1.2 on a Win32).  JUST LIKE ANY OTHER LINUX PROCESS w/ big memory page 
support.  Java can take up to a theoretical 2^64 on a 64 bit system if 
you run the 64-bit VM and pass the -b64 flag.  With parallel GC and 
other great features Java 5+ is VERY enterprise capable.

I've helped install both JBoss and Java on the largest intranet site in 
the world (which exceeds the number of users of most Internet sites) -- 
granted it was Solaris, at major financial institutions, major industry 
sites and more.  Java is already in the Enterprise and runs probably 
about 1/2 the enterprise sites out there.

BTW BEA has had a 64 bit VM for over 4 years.

-Andy

Tim Jowers wrote:
>   Ideas: One other silly but possible thing is to try to start another 
> Java
> app than JBoss. Java is not enterprise-ready yet with its mem size and is
> basically limited to 3G of user space per VM so you have to run several
> instances on large RAM machines (at least that's what a BEA consultant 
> told
> me ;-).  Also, does "sync" help to free up any space? You can also set
> swapoff to speed up the problem or even limit the RAM during boot with a
> kernel parameter in GRUB etc. Last of all, in BEA a few years back I 
> saw a
> mem alloc exception which was actually due to a mismatch between the AIX
> system calls and the java runtime code. We just changed the Java code to
> execute another set of system calls.
>
> TimJowers
>
>
> On 3/29/07, Len Boyle <Len.Boyle at sas.com> wrote:
>>
>> How much swap space do you have defined on disk?
>> On Solaris the os reserve space in main memory for possible swap 
>> usage if
>> there is none available on disk. I do not know if Red Hat does the same
>> thing, but it is something that you might look at.
>>
>> len
>>
>> -----Original Message-----
>> From: trilug-bounces at trilug.org [mailto:trilug-bounces at trilug.org] On
>> Behalf Of Robert Dale
>> Sent: Thursday, March 29, 2007 2:18 PM
>> To: Triangle Linux Users Group discussion list
>> Subject: Re: [TriLUG] Memory Monitor on a Redhat system
>>
>> On 3/29/07, Tom Le <t.thanhcle at gmail.com> wrote:
>> > We are having problems with memory usage on a Redhat AS 4 - on a
>> > 64-bit Power PC IBM pSeries. We was wondering if there is a reliable
>> > package to monitor memory usage on the server. Our current problem is
>> > that the system memory is 95% capacity and we have no idea what is
>> > taking up all the memory. We are certain that oracle is using 1G out
>> > of 16G of the box, and one instance of jboss is set to use max 1G of
>> > memory. We are trying to add a second instance of jboss and it won't
>> > start due to insufficient memory. We need a package or a way to drill
>> > down to what application using how much memory on the server Any
>> > suggestion is appreciated.
>>
>> When you say at 95% capacity is that including buffers and cache?
>>
>> What's your actual memory usage?  (/proc/meminfo would be useful here)
>> MemTotal - MemFree - Buffers - Cached = actual used memory
>>
>> What's the actual jboss error message?  Do you have the jvm stacktrace?
>> What jvm are you using?  What jvm options are you starting jboss with?
>>
>> -- 
>> Robert Dale
>> -- 
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