Performance tuning via sysctl, what is the difference between setting net.core.rmem_default (r/w) / net.ipv4.tcp_mem / net.ipv4.udp_mem

Question

What is the difference between setting read/write mem default via net/core and setting the protocol min/max/default net/ipv4 in sysctl?

Detailed explanation or resource request

net.core.wmem_default
net.core.rmem_default
net.ipv4.tcp_mem
net.ipv4.udp_mem

Thanks

Answer 1

Take a look at https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt https://www.kernel.org/doc/Documentation/sysctl/net.txt

net.ipv4.tcp_mem and net.ipv4.udp_mem limit total kernel memory for tcp and udp respectively, where as others control per socket buffer space