CODEWITHSUNDEEP
linuxubuntuapache2ram
MarcSerra
MarcSerra

Reputation: 34

Why so much difference in memory used per process in apache2 between two different systems?

I have a pair of Ubuntu dedicated servers...

Server1:

Ubuntu 16.04.7 (64 bits)
16GB RAM
8 Xeon CPU
Apache 2.4.18
MPM mode: prefork

Server2:

Ubuntu server 20.04.2 (64 bits)
32GB RAM
8 Xeon CPU
2.4.41
MPM mode: event

On Server1, each apache2 process uses between 7MB and 18MB of RAM ...

ps axo 'user rss cmd' | grep apache | grep -v "\(root\|grep\|tomcat\)"
www-data 18232 /usr/sbin/apache2 -k start
www-data 11700 /usr/sbin/apache2 -k start
www-data 11276 /usr/sbin/apache2 -k start
www-data 10792 /usr/sbin/apache2 -k start
www-data 11216 /usr/sbin/apache2 -k start
www-data 11600 /usr/sbin/apache2 -k start
www-data 10336 /usr/sbin/apache2 -k start
www-data 11356 /usr/sbin/apache2 -k start
www-data 11348 /usr/sbin/apache2 -k start
www-data 10980 /usr/sbin/apache2 -k start
www-data 11316 /usr/sbin/apache2 -k start
www-data  6808 /usr/sbin/apache2 -k start

On Server2, each apache2 process uses between 120MB and 130MB of RAM ...

ps axo 'user rss cmd' | grep apache | grep -v "\(root\|grep\|tomcat\)"
www-data 120436 /usr/sbin/apache2 -k start
www-data 119784 /usr/sbin/apache2 -k start
www-data 128720 /usr/sbin/apache2 -k start
www-data 130208 /usr/sbin/apache2 -k start

Why so much difference in memory used?

After read a few documentation and googleing, I thought about loaded modules, but there are not a lot of difference between each server...

Server1

# apache2 -M                 
Loaded Modules:
 core_module (static)
 so_module (static)
 watchdog_module (static)
 http_module (static)
 log_config_module (static)
 logio_module (static)
 version_module (static)
 unixd_module (static)
 access_compat_module (shared)
 actions_module (shared)
 alias_module (shared)
 auth_basic_module (shared)
 auth_digest_module (shared)
 auth_openidc_module (shared)
 authn_core_module (shared)
 authn_file_module (shared)
 authz_core_module (shared)
 authz_host_module (shared)
 authz_user_module (shared)
 autoindex_module (shared)
 bw_module (shared)
 cgi_module (shared)
 dav_module (shared)
 dav_fs_module (shared)
 dav_lock_module (shared)
 deflate_module (shared)
 dir_module (shared)
 env_module (shared)
 expires_module (shared)
 fcgid_module (shared)
 filter_module (shared)
 headers_module (shared)
 include_module (shared)
 mime_module (shared)
 mpm_prefork_module (shared)
 negotiation_module (shared)
 proxy_module (shared)
 proxy_balancer_module (shared)
 proxy_fcgi_module (shared)
 proxy_http_module (shared)
 rewrite_module (shared)
 setenvif_module (shared)
 slotmem_shm_module (shared)
 socache_shmcb_module (shared)
 ssl_module (shared)
 status_module (shared)
 suexec_module (shared)
 userdir_module (shared)

Server2

# apache2 -M
Loaded Modules:
 core_module (static)
 so_module (static)
 watchdog_module (static)
 http_module (static)
 log_config_module (static)
 logio_module (static)
 version_module (static)
 unixd_module (static)
 access_compat_module (shared)
 aclr_module (shared)
 actions_module (shared)
 alias_module (shared)
 auth_basic_module (shared)
 auth_digest_module (shared)
 auth_openidc_module (shared)
 authn_core_module (shared)
 authn_file_module (shared)
 authz_core_module (shared)
 authz_host_module (shared)
 authz_user_module (shared)
 autoindex_module (shared)
 cgid_module (shared)
 dav_module (shared)
 dav_fs_module (shared)
 dav_lock_module (shared)
 deflate_module (shared)
 dir_module (shared)
 env_module (shared)
 fcgid_module (shared)
 filter_module (shared)
 headers_module (shared)
 include_module (shared)
 mime_module (shared)
 mpm_event_module (shared)
 negotiation_module (shared)
 proxy_module (shared)
 proxy_balancer_module (shared)
 proxy_fcgi_module (shared)
 proxy_http_module (shared)
 remoteip_module (shared)
 reqtimeout_module (shared)
 rewrite_module (shared)
 security2_module (shared)
 setenvif_module (shared)
 slotmem_shm_module (shared)
 socache_shmcb_module (shared)
 ssl_module (shared)
 status_module (shared)
 suexec_module (shared)
 unique_id_module (shared)
 userdir_module (shared)

I already changed MPM mode from Event to Prefork on Server2, with the same results.

What else can I check to understand this difference?

Upvotes: 0

Views: 434

Answers (1)

MarcSerra
MarcSerra

Reputation: 34

The problem was with the module security2.

With the module enabled (120-160MB per process) ...

# ps axo 'user rss cmd' | grep apache | grep -v "\(root\|grep\|tomcat\)"
www-data 121232 /usr/sbin/apache2 -k start
www-data 120596 /usr/sbin/apache2 -k start
www-data 156816 /usr/sbin/apache2 -k start
www-data 162668 /usr/sbin/apache2 -k start

With the module disabled (9-15MB per process) ...

# a2dismod security2
Module security2 disabled.
To activate the new configuration, you need to run:
  systemctl restart apache2
# systemctl restart apache2
# ps axo 'user rss cmd' | grep apache | grep -v "\(root\|grep\|tomcat\)"
www-data 10340 /usr/sbin/apache2 -k start
www-data  9764 /usr/sbin/apache2 -k start
www-data 14164 /usr/sbin/apache2 -k start
www-data 14220 /usr/sbin/apache2 -k start

You can follow an email conversation here: http://mail-archives.apache.org/mod_mbox/httpd-users/202105.mbox/%3CCAD41RFYjd3XcAEqopgVWKQUnsiv9NCHRLGTM0tEOD4Kg8%2B_2hA%40mail.gmail.com%3E

Upvotes: 1

Related Questions