id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	uname	nginx_version
2365	reload increases memory used (freed memory for config is not released back to the system)	drmuey@…		"Seen on 1.18.x && 1.23.x acrocc 5 OSs (noted below in the semi-solution section)

= Problem

nginx reload (sig hub) makes a second copy of the config (which takes more memory), does its thing, and frees the memory used by the second copy. Unfortunately, it is not released it back to the system (it does reuse it as needed, for example, on a subsequent reload). 

The bigger the config the bigger the growth.

== In action

# hard restart ➜ RSS 1500 {{{ps aux | grep nginx}}}
# nginx -s reload ➜ RSS 5588
# nginx -s reload ➜ RSS 5612
# nginx -s reload ➜ RSS 5616
# hard restart ➜ RSS 1500

**Note**: this holds true w/ other forms of reload since its all essential sig hup:

* {{{/bin/kill -s HUP $(cat /var/run/nginx.pid)}}}
* {{{service nginx reload}}}

= Attempts to address

These did not have any effect:

* use mmap as memory allocator
* use tcmalloc as memory allocator
* build with no compiled in modules

One solution that did work for CentOS 7 and CloudLinux 6 (but had no effect on Ubuntu 20.04, AlmaLinux 8, or CloudLinux 6) was to use jemalloc.

On C7:

# hard restart ➜ RSS 5304
# nginx -s reload ➜ RSS 9660
# hard restart ➜ RSS 5304
# {{{LD_PRELOAD=""/usr/lib64/libjemalloc.so.1"" nginx -c reload}}} ➜ RSS 5304

uname -a for C7:

{{{Linux 10-2-67-42.cprapid.com 3.10.0-1160.25.1.el7.x86_64 #1 SMP Wed Apr 28 21:49:45 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux}}}
"	defect	new	major		nginx-core			reload memory		Linux k1.lab 5.4.0-117-generic #132-Ubuntu SMP Thu Jun 2 00:39:06 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux	"nginx version: nginx/1.18.0 (Ubuntu)
built with OpenSSL 1.1.1f  31 Mar 2020
TLS SNI support enabled
configure arguments: --with-cc-opt='-g -O2 -fdebug-prefix-map=/build/nginx-7KvRN5/nginx-1.18.0=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC -Wdate-time -D_FORTIFY_SOURCE=2' --with-ld-opt='-Wl,-Bsymbolic-functions -Wl,-z,relro -Wl,-z,now -fPIC' --prefix=/usr/share/nginx --conf-path=/etc/nginx/nginx.conf --http-log-path=/var/log/nginx/access.log --error-log-path=/var/log/nginx/error.log --lock-path=/var/lock/nginx.lock --pid-path=/run/nginx.pid --modules-path=/usr/lib/nginx/modules --http-client-body-temp-path=/var/lib/nginx/body --http-fastcgi-temp-path=/var/lib/nginx/fastcgi --http-proxy-temp-path=/var/lib/nginx/proxy --http-scgi-temp-path=/var/lib/nginx/scgi --http-uwsgi-temp-path=/var/lib/nginx/uwsgi --with-debug --with-compat --with-pcre-jit --with-http_ssl_module --with-http_stub_status_module --with-http_realip_module --with-http_auth_request_module --with-http_v2_module --with-http_dav_module --with-http_slice_module --with-threads --with-http_addition_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_image_filter_module=dynamic --with-http_sub_module --with-http_xslt_module=dynamic --with-stream=dynamic --with-stream_ssl_module --with-mail=dynamic --with-mail_ssl_module"