OK, so it’s effectively an embedded system scenario, with a fixed config 
hardware, or similar
No silver bullets or one-liner fixes here :-\

You’ve a number of options to slim down your memory footprint
- Strip Debian of all the packages you don’t need, learn a lot about kernel 
tuning, and tune the kernel to your needs.
- Start looking at one of the more embedded systems oriented distros, rather 
than OOTB Debian. Although Debian is skinnier than most, there’s a lot that can 
be done to minimise footprint. The fact that you’ve got a 64bit Debian9 running 
on it makes me fairly optimistic that you could run pretty much any Debian 
derivative.
- Profiling your userspace software stack and see if there are any dependencies 
you don’t need, strip them out. Whether you can do this will very much depend 
on the modularity of the components.

All of the above lead you down the path of maintaining forks and compiling your 
own packages, to a greater or lesser extent. That’s a maintenance overhead you 
want to avoid unless you have to.
Having said all that, if you’re looking at deploying thousands of units, the 
economics of software maintenance may stack up for you.

HTH
Dariush


> On 25 Jun 2018, at 14:32, Alex K <rightkickt...@gmail.com> wrote:
> 
> Let me change the posting style... :)
> 
> On Mon, Jun 25, 2018 at 3:51 PM, Dariush Marsh-Mossadeghi 
> <dari...@gravitas.co.uk <mailto:dari...@gravitas.co.uk>> wrote:
> OK, so we’re moving from bottom-posting to top-posting… that’ll make it 
> interesting for other readers ;-)
> 
> The output of free doesn’t look desperate, but it is starting to look a bit 
> tight.
> You’ve got about a gig of buffer/cache, which the kernel will evict if it 
> needs it.
> You’ve got 200M of genuinely free memory.
> What is potentially a little concerning is the gig of swap in use, that may 
> or may not be a problem depending on what else is running on the box and how 
> it’s memory use varies over time.
> 
> I’m not intimatley familiar with the internals of uacctd’s mysql plugins, but 
> my advice would be:
> 
> - Monitor the memory usage. If it doesn’t vary much over time you could go on 
> for years and be just fine. Keep a close watch on swap usage, if that varies 
> a lot or grows over time you’ll want to do something about it.
> Monitoring of last 2 weeks is showing that free mem is fluctuating form 50M 
> to 220 MB and swaps remains steady. Thats why I am trying to find a solution.
> 
> 
> - Read up on OOM Killer, what it does and how it behaves. If you see OOM 
> Killer entries in your logs, it’s time to think again
> I am aware of that. thanx
> 
> - Can you put some more memory in the box? 8GB of RAM will cost you about 
> £60. How much is your time worth ?
> This is not an option. What I have is 4 GB. This is not just a personal 
> project. There are going to be thousands of such installations
> 
> HTH
> Dariush
> 
> 
>> On 25 Jun 2018, at 12:32, Alex K <rightkickt...@gmail.com 
>> <mailto:rightkickt...@gmail.com>> wrote:
>> 
>> Thanx for the reply.
>> 
>> The output of free is the following:
>> 
>> free
>>             total        used        free        shared     buff/cache   
>> available
>> Mem:        4046572     2832576      152012      784240     1061984      
>> 204248
>> Swap:       3906556     1086080     2820476
>> 
>> While is as below when stopped:
>> 
>> free
>>               total        used        free      shared  buff/cache   
>> available
>> Mem:        4046572      520352     3223884       14916      302336     
>> 3286952
>> Swap:       3906556      485040     3421516
>> 
>> Seems that mysql plugins are reserving quite some memory as they list first 
>> in htop when sorted with memory.
>> 
>> Thanx,
>> Alex
>> 
>> 
>> On Mon, Jun 25, 2018 at 2:22 PM, Dariush Marsh-Mossadeghi 
>> <dari...@gravitas.co.uk <mailto:dari...@gravitas.co.uk>> wrote:
>> 
>>> On 25 Jun 2018, at 11:54, Alex K <rightkickt...@gmail.com 
>>> <mailto:rightkickt...@gmail.com>> wrote:
>>> 
>>> Hi all,
>>> 
>>> I have a setup with uacctd monitoring traffic of several interfaces through 
>>> NFLOG.
>>> With uacctd stopped I see that the server (a relatively small device with 4 
>>> GB of RAM) consumes 450MB of RAM. Once I start uacctd the mem usage goes up 
>>> to 3.5 GB. I am using mysql plugin and this is running on Debian9 64 bit.
>>> 
>>> Is there any tweaks I can use to put a limit on the memory usage of uacctd.
>>> 
>>> Thanx,
>>> Alex
>>> _______________________________________________
>>> pmacct-discussion mailing list
>>> http://www.pmacct.net/#mailinglists <http://www.pmacct.net/#mailinglists>
>> 
>> tldr; post the output of the free command when uacctd is running and I’ll do 
>> my best to interpret it for you :-)
>> 
>> Is it _really_ using it, or is it just not completely unused?
>> 
>> The linux kernel generally does pretty good job of keeping stuff that might 
>> be useful in memory, but getting rid of it very very quickly if the space is 
>> needed for something else.
>> The challenge you face is that most of the userspace tools come with a long 
>> list of caveats about what they appear to report vs what’s really happening, 
>> this is mainly due to the way the kernel shares memory between processes, 
>> and its use of as much memory as possible for various caches.
>> 
>> Some threads worth reading if you’re not familiar with the in’s and out’s of 
>> linux kernel memory management...
>> 
>> https://www.linuxatemyram.com/ <https://www.linuxatemyram.com/>
>> https://stackoverflow.com/questions/4802481/how-to-see-top-processes-sorted-by-actual-memory-usage
>>  
>> <https://stackoverflow.com/questions/4802481/how-to-see-top-processes-sorted-by-actual-memory-usage>
>> https://stackoverflow.com/questions/3784974/want-to-know-whether-enough-memory-is-free-on-a-linux-machine-to-deploy-a-new-app/
>>  
>> <https://stackoverflow.com/questions/3784974/want-to-know-whether-enough-memory-is-free-on-a-linux-machine-to-deploy-a-new-app/>
>> 
>> HTH
>> Dariush
> 

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