having 1.5GB RAM I cannot allocate more than 512MB RAM in 4.10

[dkouroun at cc.uoi.gr]

This is the output of my ulimit:

#ulimit -a | grep data
data seg size         (kbytes, -d) 524288
#

So what is next?
Is it possible to embed that information in the kernel? 
Or, how is this information set by default? Is there any specific
.conf file I should edit?

Thank you all!