apache 2.2 - Memory Ram too high in HTTPD processes

I management two dedicated servers. I use Centos 6 with Plesk Panel. Update: I use Apache with mod_php.

On the first server I have a site in Wordpress.

I have noticed that my httpd processes take up more memory each time. Besides the 'top' command, I use the following command to find out:

ps -ylC httpd --sort:rss

Image:

Pay attention to the RSS column. The httpd processes from 13MB to 127MB occupy in ram.

Installed apache modules are:

# Httpd l 
Compiled in modules: 
   core.c 
   prefork.c 
   http_core.c 

   mod_so.c 

On the second server I have a website PHPBB.

In this case the involved processes like httpd. All occupy about 85MB.

Image:

I've read that should occupy 20MB. How I can profiling or optimize this? With what tool? Xhprof I tried, but it says that the memory used is less than that then use really ...

My memory are intensive in my servers. This is a big problem.

Update:

Server 1 Meminfo output:

#cat /proc/meminfo

MemTotal:        5969120 kB
MemFree:          625720 kB
Buffers:          218424 kB
Cached:          3289320 kB
SwapCached:        61020 kB
Active:          2832624 kB
Inactive:        2066428 kB
Active(anon):    1111532 kB
Inactive(anon):   343184 kB
Active(file):    1721092 kB

Inactive(file):  1723244 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:       1959920 kB
SwapFree:        1789764 kB
Dirty:              1044 kB
Writeback:             0 kB
AnonPages:       1348048 kB
Mapped:            53712 kB
Shmem:             63408 kB

Slab:             379972 kB
SReclaimable:     220388 kB
SUnreclaim:       159584 kB
KernelStack:        2064 kB
PageTables:        28848 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     4944480 kB
Committed_AS:    3148736 kB

VmallocTotal:   34359738367 kB
VmallocUsed:       24764 kB
VmallocChunk:   34359713428 kB
HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB

DirectMap4k:     6291456 kB
DirectMap2M:           0 kB

Server 1 pmap of the httpd most memory processes (127mb and 118mb):

# pmap 11737
11737:   /usr/sbin/httpd
 total                0K
# pmap 12099

12099:   /usr/sbin/httpd
 total                0K

Server 2 Meminfo output:

# cat /proc/meminfo
MemTotal:       10088968 kB
MemFree:         1773488 kB
Buffers:          237064 kB

Cached:          5752804 kB
SwapCached:        38764 kB
Active:          4516332 kB
Inactive:        2738344 kB
Active(anon):    1028388 kB
Inactive(anon):   267156 kB
Active(file):    3487944 kB
Inactive(file):  2471188 kB
Unevictable:           0 kB
Mlocked:               0 kB

SwapTotal:       1959920 kB
SwapFree:        1883656 kB
Dirty:              4444 kB
Writeback:             0 kB
AnonPages:       1226476 kB
Mapped:            37020 kB
Shmem:             30736 kB
Slab:             862964 kB
SReclaimable:     762056 kB
SUnreclaim:       100908 kB

KernelStack:        2424 kB
PageTables:        57564 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     7004404 kB
Committed_AS:    2753212 kB
VmallocTotal:   34359738367 kB
VmallocUsed:       42048 kB
VmallocChunk:   34359642628 kB

HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:    10485760 kB
DirectMap2M:           0 kB

Server 2 httpd pmap:

# pmap 29772
29772:   /usr/sbin/httpd
 total                0K