[linux-help] Re: kernel not freeing memory.

[Jeff Vian <jvian10@xxxxxxxx>]

Weqaar Ali Janjua wrote:
> 
> Hi,
>  My linux box is running 2.2.18 kernel recompiled(non-modular) with openwall
> and lids patches. Kernel does'nt seem to free memory after running a
> process, supposing free memory before running any process is 28MB, the
> process takes up 20MB additional memory and after the process terminates the
> kernel does'nt seem to free memory instead shows 48MB in use. Any hint???
> Thanx.
> 
> ----------------------------------
> A DREAM IS A GOAL WITH A DEADLINE!
> Weqaar Ali Janjua
> B.S.Computer Engineering
> WSU
> ----------------------------------
> 
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I believe the memory is actually idle and available, just not marked as
free in the way it is displayed for you. If you ran another process that
needed that memory it would use it.  However, you have to look at the
way memory is used. Just because a process quits does NOT mean the
memory is freed instantly.  If another instance of the same process gets
started it will use what is already in memory instead of loading it
again from the disk.  That makes things faster and much more efficient.

for example, I have a lot of processes running and starting and stopping
stuff all the time as a database server.  Yet  the results of the free
command are:

                total           used            free      shared     buffers    
cached
Mem:            513288          332912          180376         0       41728    
 87364
+/- buffers/cache               203820          309468
Swap:           524656               4          524652

As you can see, very little is swapping out of memory because swap is
virtually unused, real memory is still available, and buffers and cache
are significant.

Run the free command occasionally and see what is actually happening
over a long time. One snapshot means nothing.
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