free memory usage

free memory usage

[- Luis -]

Hi everyone, 

I got a RH7.3 box which runs a java app, but i got the problem that the app 
didn't close the session with the server, so every day i got to reset the 
server to free the memory use by all the java sessions.  The first thing i 
try, was to use a bash script to kill all the java sessions, but i find out 
that the memory was still full, so the question is:

How can i free that memory without rebooting the server?

Thanks a lot 
-- 
Luis Valencia
------------------------
With a PC, I always felt limited
by the software available.
On Unix, I am limited only by my knowledge.
--Peter J. Schoenster

Re: free memory usage

[Scott Taylor]

At 04:25 AM 05/09/03, - Luis - wrote:
>Hi everyone,
>
>I got a RH7.3 box which runs a java app, but i got the problem that the app
>didn't close the session with the server, so every day i got to reset the
>server to free the memory use by all the java sessions.  The first thing i
>try, was to use a bash script to kill all the java sessions, but i find out
>that the memory was still full, so the question is:
>
>How can i free that memory without rebooting the server?


Fix the Java App.

Re: free memory usage

[Mikel Bauer]

Is memory still technically "full" (used), or is it cached?  Usually the 
kernel is smart enough to fix problems like that, and will free memory 
that's no longer being referenced (memory leaks really only exist if an 
app is still running, the kernel wont take away memory from a running app)

I would take a look at your /proc/meminfo, and see if most of the "used" 
memory is accounted for in the cache.

-- 
Mikel Bauer
mikel@bridgeband.net

- Luis - wrote:
> Hi everyone, 
> 
> I got a RH7.3 box which runs a java app, but i got the problem that the app 
> didn't close the session with the server, so every day i got to reset the 
> server to free the memory use by all the java sessions.  The first thing i 
> try, was to use a bash script to kill all the java sessions, but i find out 
> that the memory was still full, so the question is:
> 
> How can i free that memory without rebooting the server?
> 
> Thanks a lot 

Re: free memory usage

[- Luis -]

And what about if the mem is being cached or buffered? what can i do about it? 
can i free it?

Thanks

On Friday 09 May 2003 17:46, Mikel Bauer wrote:
> Is memory still technically "full" (used), or is it cached?  Usually the
> kernel is smart enough to fix problems like that, and will free memory
> that's no longer being referenced (memory leaks really only exist if an
> app is still running, the kernel wont take away memory from a running app)
>
> I would take a look at your /proc/meminfo, and see if most of the "used"
> memory is accounted for in the cache.

-- 
Luis Valencia
------------------------
With a PC, I always felt limited
by the software available.
On Unix, I am limited only by my knowledge.
--Peter J. Schoenster

Re: free memory usage

[Richard Nairn]

There is no reason to do anything about memory being used by cached or
buffered. That is automatic, and it speeds up your system. 

As far as memory leaks go, if you shut down and restart the program, the
memory will be recovered. Otherwise find the problem and fix it. 

On Fri, May 09, 2003 at 02:58:56PM +0000, - Luis - wrote:
> And what about if the mem is being cached or buffered? what can i do about it? 
> can i free it?
> 
> Thanks
> 
> On Friday 09 May 2003 17:46, Mikel Bauer wrote:
> > Is memory still technically "full" (used), or is it cached?  Usually the
> > kernel is smart enough to fix problems like that, and will free memory
> > that's no longer being referenced (memory leaks really only exist if an
> > app is still running, the kernel wont take away memory from a running app)
> >
> > I would take a look at your /proc/meminfo, and see if most of the "used"
> > memory is accounted for in the cache.
> 
> -- 
> Luis Valencia
> ------------------------
> With a PC, I always felt limited
> by the software available.
> On Unix, I am limited only by my knowledge.
> --Peter J. Schoenster
> 
> 
> -
> To unsubscribe from this list: send the line "unsubscribe linux-admin" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
---end quoted text---

-- 
|       Richard Nairn          Specializing in Linux
|     Nairn Consulting         Web / Database Solutions
|        Calgary, AB           
| Richard@NairnConsulting.ca

Re: free memory usage

[Mikel Bauer]

Memory that is buffered or cached is not the same as being used.  It is 
memory that was used before, freed, but with the possibility of being 
used again so as to speed up information retrieval.  This memory is 
available to whatever needs it.  There probably isn't a server in 
existance that doesn't cache a fair bit of memory (unless it was never 
used).

- Luis - wrote:
> And what about if the mem is being cached or buffered? what can i do about it? 
> can i free it?
> 
> Thanks
> 
> On Friday 09 May 2003 17:46, Mikel Bauer wrote:
> 
>>Is memory still technically "full" (used), or is it cached?  Usually the
>>kernel is smart enough to fix problems like that, and will free memory
>>that's no longer being referenced (memory leaks really only exist if an
>>app is still running, the kernel wont take away memory from a running app)
>>
>>I would take a look at your /proc/meminfo, and see if most of the "used"
>>memory is accounted for in the cache.
> 
> 

-- 
Mikel Bauer

Re: free memory usage

[Glynn Clements]

- Luis - wrote:

> I got a RH7.3 box which runs a java app, but i got the problem that the app 
> didn't close the session with the server, so every day i got to reset the 
> server to free the memory use by all the java sessions.  The first thing i 
> try, was to use a bash script to kill all the java sessions, but i find out 
> that the memory was still full, so the question is:
> 
> How can i free that memory without rebooting the server?

First, are you sure that the memory isn't being released? Or are you
misreading the memory statistics? In the output from "free", the
relevant numbers are those on the second row; e.g. here:

             total       used       free     shared    buffers     cached
Mem:        257572     103312     154260          0       3640      48164
-/+ buffers/cache:      51508     206064 
Swap:       262136          0     262136

the relevant number is 206064. The numbers on the first row (e.g. 
154260 above) aren't relevant.

OTOH, if the server really is running out of memory, even when the
clients are being killed, the only solutions are to either:

a) re-write the daemon which is using up all of the memory, or
b) forcibly restart the daemon at regular intervals (you don't need to
reboot the entire server, and doing so won't acheive anything).

-- 
Glynn Clements <glynn.clements@virgin.net>

Re: free memory usage

[- Luis -]

Thanks, let me take a closer look at the mem stat, because i was only looking 
at the info from top command, but in fact im restarting the deamon that get 
the app up, and the free mem field from 'top' is still showing a lot of 
memory used.

On Friday 09 May 2003 17:55, Glynn Clements wrote:
> - Luis - wrote:
> > I got a RH7.3 box which runs a java app, but i got the problem that the
> > app didn't close the session with the server, so every day i got to reset
> > the server to free the memory use by all the java sessions.  The first
> > thing i try, was to use a bash script to kill all the java sessions, but
> > i find out that the memory was still full, so the question is:
> >
> > How can i free that memory without rebooting the server?
>
> First, are you sure that the memory isn't being released? Or are you
> misreading the memory statistics? In the output from "free", the
> relevant numbers are those on the second row; e.g. here:
>
>              total       used       free     shared    buffers     cached
> Mem:        257572     103312     154260          0       3640      48164
> -/+ buffers/cache:      51508     206064
> Swap:       262136          0     262136
>
> the relevant number is 206064. The numbers on the first row (e.g.
> 154260 above) aren't relevant.
>
> OTOH, if the server really is running out of memory, even when the
> clients are being killed, the only solutions are to either:
>
> a) re-write the daemon which is using up all of the memory, or
> b) forcibly restart the daemon at regular intervals (you don't need to
> reboot the entire server, and doing so won't acheive anything).

-- 
Luis Valencia
------------------------
With a PC, I always felt limited
by the software available.
On Unix, I am limited only by my knowledge.
--Peter J. Schoenster

Re: free memory usage

[jbrown105]

On Fri, May 09, 2003 at 11:25:31AM +0000, - Luis - wrote:
> Hi everyone, 
> 
> I got a RH7.3 box which runs a java app, but i got the problem that the app 
> didn't close the session with the server, so every day i got to reset the 
> server to free the memory use by all the java sessions.  The first thing i 
> try, was to use a bash script to kill all the java sessions, but i find out 
> that the memory was still full, so the question is:
> 
> How can i free that memory without rebooting the server?
> 
> Thanks a lot 
> -- 
> Luis Valencia

If 'kill -SIGTERM' doesnt work, then 'kill -SIGKILL' should.

On getting a sigkill the app is required to quit and free all of its
memory (as well as close files etc).

> ------------------------
> With a PC, I always felt limited
> by the software available.
> On Unix, I am limited only by my knowledge.
> --Peter J. Schoenster
> 
> 
> -
> To unsubscribe from this list: send the line "unsubscribe linux-admin" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

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Re: free memory usage

[Glynn Clements]

jbrown105@speedymail.org wrote:

> > I got a RH7.3 box which runs a java app, but i got the problem that the app 
> > didn't close the session with the server, so every day i got to reset the 
> > server to free the memory use by all the java sessions.  The first thing i 
> > try, was to use a bash script to kill all the java sessions, but i find out 
> > that the memory was still full, so the question is:
> > 
> > How can i free that memory without rebooting the server?
> 
> If 'kill -SIGTERM' doesnt work, then 'kill -SIGKILL' should.
> 
> On getting a sigkill the app is required to quit and free all of its
> memory (as well as close files etc).

More accurately: on receiving SIGKILL, the process will be forcibly
terminated, and all of its resources will be released. This doesn't
require any cooperation from the program.

-- 
Glynn Clements <glynn.clements@virgin.net>