Hi,
I have a fresh install (2 days ago) of ubuntu 12.04 because switch the old server to this but now I have a memory issue:

$ free -m
             total       used       free     shared    buffers     cached
Mem:           989        946         42          0         40        313
-/+ buffers/cache:        592        396
Swap:          511          7        504

I tried "htop" but the result of free memory is completely different:



My apache Config:

<IfModule mpm_prefork_module>
    StartServers          2
    MinSpareServers       6
    MaxSpareServers      12
    MaxClients           80
    MaxRequestsPerChild 3000
</IfModule>

My MySQL config:

key_buffer              = 32M
max_allowed_packet      = 1M
thread_stack            = 128K
thread_cache_size       = 8
# This replaces the startup script and checks MyISAM tables if needed
# the first time they are touched
myisam-recover          = BACKUP
#max_connections        = 100
table_cache             = 32
#thread_concurrency     = 10

All of my site with a DB (magento, prestashop, wordpress ecc) are really slow, I used the mysql config in your documentation and the response time was: magento 10 seconds, prestashop 5 seconds, wordpress 12 seconds.

I haven't traffic these sites, mysql work in localhost, I performed databases, file hosts look good.

Help to find the issue

You have 396MB of free RAM.

http://www.linuxatemyram.com/

Whatever database issues you're having, they have nothing to do with running out of memory.

Ok, a linode admin told me that my Linode is OOMing .. so where is the problem?

MaxClients           80

that's too high for a 1GB node, drop it to say 5 and slowly increase it until you have a balance between memory usage (the green part of bar in htop) and performance. You may need to upgrade the size of your node.

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The problem is still the same

If you go there my settings are equals to the reccomendid settings.

What recommended settings, it's unlikely you could achieve the balance in the 7 minutes between my post and yours.

_________________
Paid support
How to ask for help
1. Give details of your problem
2. Post any errors
3. Post relevant logs.
4. Don't hide details i.e. your domain, it just makes things harder
5. Be polite or you'll be eaten by a grue

I was planning to note the same thing.

I tried but nothing change (I increase maxclient 5 each time and reset apache)