Tracking memory usage?

I am just wondering if there is a way/command to track memory usage to know exactly what is using our memory.

We are on a dedicated with 1024 DDR and on the Server status, it says that Memory Used = 75 %

But on top in shell, I can see only 50% (by bnetd) of memory used. I would like to find out what is using all that memory beside bnetd...

Code: 
  PID USER     PRI  NI  SIZE  RSS SHARE STAT %CPU %MEM   TIME CPU COMMAND
 1351 mysql     15   0 30816  20M  1144 S    23.3  2.0  84:44   0 mysqld
 2429 pgtowns2  15   0 1454M 494M   548 R    11.3 49.9 212:52   0 bnetd
 2472 root      15   0  1156   96    52 S     2.3  0.0  30:27   0 httpd
  995 root      15   0   180  152   100 S     0.1  0.0   3:36   0 syslogd
27215 pgtowns2  16   0   916  916   496 R     0.1  0.0   0:00   0 top
    1 root      15   0   100   72    44 S     0.0  0.0   0:04   0 init
    2 root      15   0     0    0     0 SW    0.0  0.0   0:00   0 keventd
    3 root      15   0     0    0     0 SW    0.0  0.0   0:00   0 kapmd
    4 root      34  19     0    0     0 SWN   0.0  0.0   0:02   0 ksoftirqd_CPU0
    9 root      25   0     0    0     0 SW    0.0  0.0   0:00   0 bdflush
    5 root      15   0     0    0     0 SW    0.0  0.0   0:01   0 kswapd
    6 root      15   0     0    0     0 SW    0.0  0.0   0:00   0 kscand/DMA
    7 root      15   0     0    0     0 SW    0.0  0.0   4:45   0 kscand/Normal
    8 root      15   0     0    0     0 SW    0.0  0.0   0:44   0 kscand/HighMem
   10 root      15   0     0    0     0 SW    0.0  0.0   0:00   0 kupdated
   11 root      23   0     0    0     0 SW    0.0  0.0   0:00   0 mdrecoveryd
   15 root      15   0     0    0     0 SW    0.0  0.0   5:59   0 kjournald
  621 root      15   0     0    0     0 SW    0.0  0.0   0:00   0 kjournald
  999 root      15   0    60    4     0 S     0.0  0.0   0:00   0 klogd
 1078 named     24   0  2424 2192   632 S     0.0  0.2   0:22   0 named
 1092 root      15   0   316  180    76 S     0.0  0.0   0:04   0 sshd
 1106 root      15   0   220  148    76 S     0.0  0.0   0:00   0 xinetd
 1124 root      15   0  1664  772   368 S     0.0  0.0   0:02   0 chkservd
 1177 mailnull  15   0   412  140    60 S     0.0  0.0   0:00   0 exim
 1181 mailnull  15   0   340    4     0 S     0.0  0.0   0:00   0 exim
 1187 root      15   0   612  552   332 S     0.0  0.0   0:00   0 antirelayd
 1207 root      21   0 17936    4     0 S     0.0  0.0   0:00   0 spamd
 1249 bin       15   0   436   36     4 S     0.0  0.0   0:00   0 cannaserver
 1252 root      15   0 18516 9764     0 S     0.0  0.9   0:05   0 spamd
 1253 root      16   0 18524 9748     0 S     0.0  0.9   0:05   0 spamd
 1254 root      15   0 19200  13M   688 S     0.0  1.3   0:05   0 spamd
 1255 root      16   0 19156  10M   632 S     0.0  1.0   0:05   0 spamd
 1256 root      16   0 19208  13M   688 S     0.0  1.3   0:05   0 spamd
 1266 root      15   0    80   52     4 S     0.0  0.0   0:00   0 crond
 1283 wnn       22   0  3348    4     0 S     0.0  0.0   0:00   0 jserver
 1294 root      15   0  3328  644   256 S     0.0  0.0   0:01   0 cppop
 1297 root      25   0   156    4     0 S     0.0  0.0   0:00   0 mysqld_safe
Thanks.

 

 

 

 

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