Active Memory never reclaimed please help me understand

[Prem Kumar]

also wondering if there is a way I can list Active memory map showing me
what is cached?

-regards.

On Tue, Sep 22, 2015 at 3:08 PM, Prem Kumar <prem.it.kumar at gmail.com> wrote:

> Dear All,
>
> I have done quite a bit of reading on Active memory reported in
> /proc/meminfo and in short says it is never reclaimed unless absolutely
> necessary, and it caches the recently used files/pages in memory. Although
> I fail to understand the consequences that I face here.
>
> I have disk-less and swap-less nodes. So all I have to do, is play with
> the RAM on the box. Issue that brought me here is investigating why after
> running some applications, used memory is never available for use with any
> other applications.
>
> In other words I cannot run any programs that requests memory more than
> what is shown as free in the output of free command and MemFree in the
> output of the cat /proc/meminfo
> For example if I ran any program that requires more than 6GB on the first
> node below and more than 1GB on the second node below they fail instantly,
> and work fine if within the limist of free. There is nothing else running
> on the system other than system processes/services.
>
>              total       used       free     shared    buffers     cached
> Mem:            23         17          6          0          0          9
> -/+ buffers/cache:          8         15
> Swap:            0          0          0
>
>              total       used       free     shared    buffers     cached
> Mem:            23         22          1          0          0          0
> -/+ buffers/cache:         21          1
> Swap:            0          0          0
>
> Since the applications that ran previously are not running any more "even
> though they died out of memory because they requested more memory than
> available", shouldn't the OS see that any memory used previously as useless
> and can it not reclaim that for use with the next job/program on that
> machine.
>
> On every machine that I have run into this problem the out put of
> /proc/meminfo shows that Active memory is used up the amount shown in the
> free command and limits my further runs.
>
> This is driving me insane and making me feel stupid knowing that OS is
> smart enough to handle this, then what am I missing here to understand?
> Please advise.
>
> Appreciate any insight into this.
>
> Best Regards,
> Prem
>
>
>
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