Troubleshoot Memory usage

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Troubleshooting memory usage

A better checklist can be found at http://rimuhosting.com/howto/memory.jsp

Running "top" always tells you all RAM is used ? This is an example on the HG. Am I really using 124M of RAM ???

LinkStation:/media# top
top - 11:41:03 up  2:40,  1 user,  load average: 0.08, 0.14, 0.15
Tasks:  55 total,   2 running,  53 sleeping,   0 stopped,   0 zombie
Cpu(s):  4.3% us,  3.3% sy,  0.0% ni, 89.8% id,  1.6% wa,  0.3% hi,   0.7% si
Mem:    126496k total,   124636k used,     1860k free,     2928k buffers
Swap:   522104k total,    25664k used,   496440k free,    61328k cached

It doesn't tell you the right story, as you'll see below.

/var/log/messages

Look for any "Out of memory" logs. You should not have any.

free -m

Any_Linux_box# free -m
total    used   free    shared buffers cached
Mem:        90      85       4      0       3       34
-/+ buffers/cache:  46      43
Swap:       9        0       9 

The top row 'used' (85) value will almost always nearly match the top row mem value (90). Since Linux likes to use any spare memory to cache disk blocks (34).The key figure to look at is the buffers/cache row used value (46). This is how much space your applications are currently using. For best performance, this number should be less than your total (90) memory. To prevent out of memory errors, it needs to be less than the total memory (90) and swap space (9).

ps aux

LinkStation:/media# ps aux
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         1  0.0  0.4   2408   580 ?        S    09:00   0:01 init [2]
root         2  0.0  0.0      0     0 ?        SN   09:00   0:00 [ksoftirqd/0]
root         3  0.0  0.0      0     0 ?        S<   09:00   0:00 [events/0]
root         4  0.0  0.0      0     0 ?        S<   09:00   0:00 [khelper]
root         5  0.0  0.0      0     0 ?        S<   09:00   0:00 [kthread]
root        20  0.0  0.0      0     0 ?        S<   09:00   0:00 [kblockd/0]
root        23  0.0  0.0      0     0 ?        S<   09:00   0:00 [khubd]
root        56  0.0  0.0      0     0 ?        S    09:00   0:00 [pdflush]
root        57  0.0  0.0      0     0 ?        S    09:00   0:00 [pdflush]
root        59  0.0  0.0      0     0 ?        S<   09:00   0:00 [aio/0]
root        58  0.0  0.0      0     0 ?        S    09:00   0:01 [kswapd0]
root       643  0.0  0.0      0     0 ?        S<   09:00   0:00 [kseriod]
root       679  0.0  0.0      0     0 ?        S    09:00   0:00 [mtdblockd]
root       728  0.0  0.0      0     0 ?        S    09:00   0:00 [kjournald]
root       959  0.0  0.0      0     0 ?        S    09:00   0:02 [kjournald]
root      1341  0.5  0.1   1812   140 ?        Ss   09:00   0:56 /sbin/dhcpcd-bi
root      1497  0.0  0.4   1908   600 ?        Ss   09:00   0:00 /sbin/syslogd -
root      1503  0.0  0.2   1796   316 ?        Ss   09:00   0:00 /sbin/klogd
root      1509  0.0  0.3   1776   460 ?        Ss   09:00   0:00 /usr/sbin/ppc_u
root      1532  0.0  0.1   2184   128 ?        S    09:00   0:00 /usr/sbin/ap_se
root      1546  0.0  0.9   3464  1152 ?        S    09:00   0:00 /bin/sh /usr/bi
mysql     1607  0.0  8.6 130476 11000 ?        Sl   09:00   0:09 /usr/sbin/mysql
root      1608  0.0  0.4   1776   508 ?        S    09:00   0:00 logger -p daemo
root      1686  0.0  0.4   2384   520 ?        Ss   09:00   0:00 /usr/sbin/dropb
root      1707  0.0  2.2   7632  2848 ?        S    09:00   0:03 ddclient - slee
102       1719  0.0  0.4   7088   532 ?        Ss   09:01   0:00 /usr/sbin/exim4
root      1725  0.0  0.2   1784   320 ?        Ss   09:01   0:00 /usr/sbin/inetd
www-data  1731  0.0  1.0   5956  1328 ?        S    09:01   0:00 /usr/sbin/light
www-data  1736  0.0  3.7  17968  4796 ?        Ss   09:01   0:00 /usr/bin/php5-c
mldonkey  1742  9.6 28.9  48704 36672 ?        Sl   09:01  15:49 /home/mldonkey/
www-data  1760  0.0  1.5  17968  1916 ?        S    09:01   0:00 /usr/bin/php5-c
www-data  1761  0.0  1.5  17968  1916 ?        S    09:01   0:00 /usr/bin/php5-c
www-data  1762  0.0  1.5  17968  1916 ?        S    09:01   0:00 /usr/bin/php5-c
www-data  1763  0.0  1.5  17968  1912 ?        S    09:01   0:00 /usr/bin/php5-c
nut       1764  0.0  0.4   2440   568 ?        Ss   09:01   0:02 /lib/nut/newhid
nut       1766  0.0  0.3   2292   432 ?        Ss   09:01   0:00 /sbin/upsd
root      1768  0.0  0.4   2284   568 ?        Ss   09:01   0:00 /sbin/upsmon
nut       1769  0.0  0.4   2284   580 ?        S    09:01   0:00 /sbin/upsmon
root      1772  0.0  0.7   7748   968 ?        Ss   09:01   0:00 /usr/sbin/nmbd
root      1774  0.0  0.5  11056   744 ?        Ss   09:01   0:00 /usr/sbin/smbd
root      1780  0.0  0.3   1776   504 ?        Ss   09:01   0:00 /home/myscripts
root      1783  0.0  0.3   1776   500 ?        Ss   09:01   0:00 /home/myscripts
root      1786  0.0  0.1  11056   220 ?        S    09:01   0:00 /usr/sbin/smbd
root      1797  0.1  1.0  10408  1368 ?        S    09:01   0:10 Xvnc :1 -deskto
root      1817  0.0  0.5   5148   676 ?        S    09:01   0:00 vncconfig -icon
root      1819  0.0  1.0   8360  1328 ?        S    09:01   0:04 x-window-manage
root      1856  0.0  3.2   4504  4092 ?        SLs  09:01   0:00 /usr/sbin/ntpd
daemon    1863  0.0  0.2   2452   340 ?        Ss   09:01   0:00 /usr/sbin/atd
root      1869  0.0  0.6   2992   780 ?        Ss   09:01   0:00 /usr/sbin/cron
root      1886  0.0  0.9  11016  1236 ?        Ss   09:01   0:00 /usr/bin/perl /
root      1915  0.0  0.9  11320  1204 ?        S    09:44   0:00 /usr/sbin/smbd
root      1917  0.4  2.2  11536  2800 ?        S    09:50   0:30 /usr/sbin/smbd
root      1974  0.0  0.8   2860  1024 ?        Ss   09:56   0:02 /usr/sbin/dropb
root      1975  0.0  1.4   3544  1812 pts/1    Ss   09:56   0:00 -bash
root      2290  0.0  0.7   2784   992 pts/1    R+   11:44   0:00 ps aux

The biggest RAM users here are mldonkey & mysql.

vmstat 1 2

LinkStation:/media# vmstat 1 2
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
3  0  25664   1980   2796  61316    1    3   126    37  186   355 14  4 78  4
0  0  25664   1924   2800  61348    0    0     4     0  155   354  3  2 94  1

The si (swap in) and so (swap out) columns show if you have been swapping (i.e. needing to dip into 'virtual' memory) in order to run your server's applications. The si/so numbers should be 0 (or close to it).