I confirm there is some raise in used memory after rndc reload, both in named-chroot and named service. But it increases only the first time server is reloaded, after that is keeps at the same levels.

But there are absolutly no numbers I can work with in this report.
Prepared just few data entries by this command:
yum install ldns
ldns-gen-zone -a 10000 -o test named.empty > /var/named/test.zone

cat NAMEDCONF >> /etc/named.conf
zone "test" IN {
        type master;
        file "test.zone";
};
NAMEDCONF

I used this command to test it:
$ systemctl start named-chroot && ps u -C named && rndc reload && ps u -C named
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
named    23948  0.2  4.5 233428 85144 ?        Ssl  06:38   0:00 /usr/sbin/named
server reload successful
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
named    23948  0.3  7.9 299744 150388 ?       Ssl  06:38   0:00 /usr/sbin/named

I can see significant increase in used RSS memory. But it is far from 90% as reported.

No configuration or number of zones or data were provided. No output of rndc stats is available, which should be relevant. Can it be run before reload and after it? Then contents of last parts in /var/named/data/named_stats.txt should contain some changed data.

I can search why it increases memory usage. Is customer limiting cache size by max-cache-size option to any value? How many zones and records does customer have in their configuration?

Created attachment 1553524 [details]
named_stats.txt

This reported issue is the same as older bug #1578051. Even outcome seems the same, it became issue with --tuning=large. Would be solved as single bug eventually.

*** This bug has been marked as a duplicate of bug 1578051 ***