Where is my memory gone ? ;-)

rbeserie · 05-07-2010, 06:22 AM

Hey every one.

I got a computer working ... not bad hein? it has 2GB Ram. so far so good.

"free -m" reports a little more then 250 free memory.

Quote:

$> free -m
total used free shared buffers cached
Mem: 2028 1767 260 0 309 906
-/+ buffers/cache: 551 1476
Swap: 1906 0 1906

on the other hand, "ps -A u" gives me the list of all the runing processes and the memory each one uses.

Quote:

$> ps -A u
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 0.0 1848 592 ? Ss 2009 1:04 init [2]
nagios 9279 0.0 0.5 40228 10552 ? Sl 2009 180:08 /usr/bin/perl -w /opt/centreon/ODS/ods
root 1611 0.0 0.0 3696 992 ? Ss Apr08 0:04 /usr/sbin/cron
root 10904 0.0 0.0 5416 1020 ? Ss Apr08 0:00 /usr/sbin/sshd
bind 13912 0.0 0.9 59940 18808 ? Ssl Apr08 0:48 /usr/sbin/named -u bind
snmp 14272 0.0 0.2 10620 4224 ? S Apr08 0:02 /usr/sbin/snmpd -Lsd -Lf /dev/null -u snmp -I -smux -p /var/run/snmpd.pid 127.0.0.1
root 16127 0.0 0.0 4132 1276 ? S Apr08 0:00 /bin/sh /usr/bin/mysqld_safe
mysql 16164 0.0 4.5 231696 95392 ? Sl Apr08 28:42 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql --pid-file=/var/run/my
root 16165 0.0 0.0 3252 612 ? S Apr08 0:00 logger -p daemon.err -t mysqld_safe -i -t mysqld
nagios 17834 0.0 0.0 2184 660 ? Ss Apr09 0:15 /usr/sbin/nsca --daemon -c /etc/nsca.cfg
root 14289 0.0 0.4 27488 9924 ? Ss Apr20 0:01 /usr/sbin/apache2 -k start
nagios 3046 0.0 0.0 2184 444 ? SL Apr21 0:00 /usr/sbin/nsca --daemon -c /etc/nsca.cfg
nagios 1875 0.1 0.1 15896 2096 ? SNsl May06 1:59 /usr/sbin/nagios3 -d /etc/nagios3/nagios.cfg
www-data 14615 0.1 0.4 27856 9472 ? S May06 1:23 /usr/sbin/apache2 -k start
www-data 24801 0.1 0.4 27864 9524 ? S 06:30 0:40 /usr/sbin/apache2 -k start
www-data 29563 0.1 0.7 34720 16584 ? S 06:45 0:41 /usr/sbin/apache2 -k start
www-data 1052 0.1 0.5 29408 11704 ? S 07:00 0:39 /usr/sbin/apache2 -k start
www-data 9969 0.2 0.4 27876 9472 ? S 07:30 0:42 /usr/sbin/apache2 -k start
www-data 18629 0.1 0.4 27856 9444 ? S 07:59 0:33 /usr/sbin/apache2 -k start
www-data 23724 0.2 0.4 27864 9452 ? S 08:15 0:32 /usr/sbin/apache2 -k start
www-data 27649 0.2 0.6 30140 12524 ? S 08:29 0:36 /usr/sbin/apache2 -k start
www-data 3974 0.2 0.4 28660 10244 ? S 08:59 0:29 /usr/sbin/apache2 -k start
www-data 8981 0.2 0.4 28644 10180 ? S 09:15 0:29 /usr/sbin/apache2 -k start
www-data 12850 0.2 0.4 28644 10144 ? S 09:29 0:28 /usr/sbin/apache2 -k start
www-data 26554 0.2 0.4 27876 9304 ? S 10:14 0:21 /usr/sbin/apache2 -k start
www-data 26594 0.2 0.5 30592 12284 ? S 10:15 0:20 /usr/sbin/apache2 -k start
root 3323 0.0 0.1 8112 2468 ? Ss 10:46 0:00 sshd: root@pts/0
root 3428 0.0 0.0 4500 1740 pts/0 Ss 10:47 0:00 -bash
www-data 7038 0.1 0.4 27856 9244 ? S 11:00 0:11 /usr/sbin/apache2 -k start
www-data 15808 0.1 0.4 28132 9456 ? S 11:29 0:07 /usr/sbin/apache2 -k start
www-data 15921 0.2 0.4 28644 9988 ? S 11:30 0:09 /usr/sbin/apache2 -k start
www-data 20768 0.2 0.4 27856 9052 ? S 11:45 0:08 /usr/sbin/apache2 -k start
www-data 24779 0.2 0.4 28644 9868 ? S 12:00 0:06 /usr/sbin/apache2 -k start
www-data 1102 0.1 0.3 27824 8280 ? S 12:29 0:01 /usr/sbin/apache2 -k start
www-data 1223 0.1 0.4 28584 9592 ? S 12:30 0:01 /usr/sbin/apache2 -k start
root 5930 0.0 0.0 3956 1032 pts/0 R+ 12:44 0:00 ps -A u

if i sum it all up I get a big 16% mem usage...
if my math is all right, 16% of 2048 is 327.
so the free mem should be : 2048 - 327 and that is : 1697MB...

nothing close to what "free" reports. so where is the rest ?

Thanks to any one having an idea to put me back on the trail of my lost memories... ;-)

AlucardZero · 05-07-2010, 08:07 AM

www.linuxatemyram.com

johnsfine · 05-07-2010, 08:33 AM

Quote:

Originally Posted by rbeserie

"ps -A u" gives me the list of all

Please use CODE tags instead of QUOTE tags for things like that. It makes a big difference in readability.

Quote:

Originally Posted by AlucardZero

www.linuxatemyram.com

Cute picture at the top, and a good newbie level answer to the question.

Quote:

Originally Posted by rbeserie

if i sum it all up I get a big 16% mem usage...
if my math is all right, 16% of 2048 is 327.
so the free mem should be : 2048 - 327 and that is : 1697MB.

Adding up the %MEM column and multiplying by total memory, is just an inaccurate way (accumulates rounding errors) of totaling the RSS column.

The total of RSS is itself a fairly bad estimate of the total memory used by all those processes (a better estimate that you get from %MEM, but still fairly bad).

So far as I know, there isn't a better estimate of that total, other than getting it from the other side (which defeats the purpose of comparing it to the other side): From the total subtract kernel memory use, cache, buffers, and free. I think the result would be the true value of what you might expect the total of RSS to represent.

drsketch1 · 02-09-2011, 08:31 AM

Linux uses ram b4 swap, which is how it should be done. Windows is finally doing this.