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Operating Systems Linux Underutilization of Linux memory Post 303044181 by Neo on Sunday 16th of February 2020 07:42:42 AM
Old 02-16-2020
And tomorrow, I will take this dedicated Ubuntu server, currently looks like this (runs MQTT, mysql, apache2 and a number of web sites, does backups, etc):

Code:
top - 06:40:25 up 35 days, 6 min,  1 user,  load average: 0.05, 0.12, 0.16
Tasks: 224 total,   1 running, 223 sleeping,   0 stopped,   0 zombie
%Cpu(s):  1.5 us,  0.9 sy,  0.0 ni, 97.5 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem : 32652952 total, 16986476 free,   694036 used, 14972440 buff/cache
KiB Swap:  7996412 total,  7996412 free,        0 used. 31071156 avail Mem 

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND                                                                                                           
  950 mysql     20   0 2749912 333616  19552 S   0.7  1.0 542:11.32 mysqld                                                                                                            
 8346 www-data  20   0  479644  32704  21104 S   0.7  0.1   0:00.02 apache2                                                                                                           
 8353 www-data  20   0  477684  24696  13064 S   0.7  0.1   0:00.02 apache2                                                                                                           
  901 www-data  20   0  343920  25120   2356 S   0.3  0.1  73:38.94 memcached                                                                                                         
 7461 www-data  20   0  477100  15708   4556 S   0.3  0.0   0:00.05 apache2                                                                                                           
 7607 www-data  20   0  477100  15708   4556 S   0.3  0.0   0:00.03 apache2                                                                                                           
 8205 www-data  20   0  477100  15708   4556 S   0.3  0.0   0:00.01 apache2                                                                                                           
    1 root      20   0  185144   5792   4040 S   0.0  0.0   2:55.18 systemd       
..
...
...
...

Will do the same... will turn off swap complete for a day and compare before and after.

In this manner, everyone can see two very different real-world, live Linux server examples of running with swap on and off; in both cases, there is plenty of memory. In fact, the server in this post (the dedicated server) shows zero swap being used even though the uptime is:

Code:
ubuntu# uptime
 06:44:46 up 35 days, 11 min,  1 user,  load average: 0.31, 0.22, 0.19

 

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APACHE2(8)							      apache2								APACHE2(8)

NAME
apache2 - Apache Hypertext Transfer Protocol Server SYNOPSIS
apache2 [ -d serverroot ] [ -f config ] [ -C directive ] [ -c directive ] [ -D parameter ] [ -e level ] [ -E file ] [ -k start|restart|graceful|stop|graceful-stop ] [ -R directory ] [ -h ] [ -l ] [ -L ] [ -S ] [ -t ] [ -v ] [ -V ] [ -X ] [ -M ] SUMMARY
apache2 is the Apache HyperText Transfer Protocol (HTTP) server program. It is designed to be run as a standalone daemon process. When used like this it will create a pool of child processes or threads to handle requests. In general, apache2 should not be invoked directly, but rather should be invoked via /etc/init.d/apache2 or apache2ctl. The default Debian configuration requires environment variables that are defined in /etc/apache2/envvars and are not available if apache2 is started directly. However, apache2ctl can be used to pass arbitrary arguments to apache2. DOCUMENTATION
The full documentation is available in the apache2-doc package or at http://httpd.apache.org/docs/2.2/ . Information about Debian specific changes and configuration can be found in /usr/share/doc/apache2/README.Debian.gz . OPTIONS
-d serverroot Set the initial value for the ServerRoot directive to serverroot. This can be overridden by the ServerRoot directive in the configu- ration file. -f config Uses the directives in the file config on startup. If config does not begin with a /, then it is taken to be a path relative to the ServerRoot. The default is /etc/apache2/apache2.conf. -k start|restart|graceful|stop|graceful-stop Signals apache2 to start, restart, or stop. See Stopping Apache for more information. -C directive Process the configuration directive before reading config files. -c directive Process the configuration directive after reading config files. -D parameter Sets a configuration parameter which can be used with <IfDefine> sections in the configuration files to conditionally skip or process commands at server startup and restart. -e level Sets the LogLevel to level during server startup. This is useful for temporarily increasing the verbosity of the error messages to find problems during startup. -E file Send error messages during server startup to file. -R directory When the server is compiled using the SHARED_CORE rule, this specifies the directory for the shared object files. -h Output a short summary of available command line options. -l Output a list of modules compiled into the server. This will not list dynamically loaded modules included using the LoadModule directive. -L Output a list of directives together with expected arguments and places where the directive is valid. -M Dump a list of loaded Static and Shared Modules. -S Show the settings as parsed from the config file (currently only shows the virtualhost settings). -t Run syntax tests for configuration files only. The program immediately exits after these syntax parsing tests with either a return code of 0 (Syntax OK) or return code not equal to 0 (Syntax Error). If -D DUMP_VHOSTS is also set, details of the virtual host con- figuration will be printed. If -D DUMP_MODULES is set, all loaded modules will be printed. -v Print the version of apache2, and then exit. -V Print the version and build parameters of apache2, and then exit. -X Run apache2 in debug mode. Only one worker will be started and the server will not detach from the console. SEE ALSO
apache2ctl(8), /usr/share/doc/apache2/README.Debian.gz Apache HTTP Server 2008-04-05 APACHE2(8)
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