Cannot disable connection tracking

I noticed there is a note in LEDE Documentation which says that disabling firewall's connection tracking can speed up routing and save memory. So I tried to disable it but that didn't work. Could someone tell me how to do it?

Thanks in advance.

What I did

I followed the guide and tried disabling it by specifying 'option conntrack 0' in /etc/config/firewall.

# cat /etc/config/firewall

config zone
    option name             awlan
    list   network          'awlan'
    option conntrack        0
    option input            REJECT
    option output           ACCEPT
    option forward          REJECT


And then, I proceeded to reload the configuration but it says the option conntrack is unknown.

# /etc/init.d/firewall reload
Warning: Option @zone[0].conntrack is unknown


As expected, there seems to be no firewall rules regarding connection tracking.

# iptables -t raw -L -vn
Chain PREROUTING (policy ACCEPT 1587 packets, 251K bytes)
 pkts bytes target     prot opt in     out     source               destination
Chain OUTPUT (policy ACCEPT 1422 packets, 326K bytes)
 pkts bytes target     prot opt in     out     source               destination

Hardware and Software

I don't know if this clarifies the issue, but I tried LEDE 17.01.2 on WZR-300HP (Buffalo) and WZR-HP-G450H (Buffalo) and both of which didn't work.

AFAIK, that's because with firewall3 it's not supported anymore. Further reading:
Wiki note:
And commit note introducing this change:

Furthermore, if you are using masquerading, you seems to require this feature anyway...

Thank you for the clear answer!

It turns out I missed the note on the page you've posted even though it is very obvious. I'm stupid...

This is now obsolete since fw3 version 2016-11-29 ...

Since disabling connection tracking seems unnecessary now according to the commit message, I decided to keep it turned on.

As for masquerading, I'm using my routers like VLAN switches so I don't need to use masquerading for now.

Thanks again for answering my question!