I am testing my web server with Jmeter. I launch 40 users test, then dump top command. What i see, is 40 (+1 host) apache processes. Each process uses appr. 7mb of RES memory. But 7*40 is 280 mb of memory. But top shows that there are 508mb total and 345mb free. So only 163mb used... Why i have such strange stuff?
top - 04:49:24 up 1 day, 10:49, 1 user, load average: 0.28, 0.18, 0.16
Tasks: 107 total, 2 running, 105 sleeping, 0 stopped, 0 zombie
Cpu(s): 1.4%us, 0.4%sy, 0.0%ni, 97.6%id, 0.5%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 508132k total, 162428k used, 345704k free, 28340k buffers
Swap: 916476k total, 21800k used, 894676k free, 63480k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
9816 www-data 20 0 69232 7260 3232 S 1.9 1.4 0:00.69 apache2
9890 www-data 20 0 69232 7260 3232 S 1.9 1.4 0:00.06 apache2
9900 www-data 20 0 69232 7260 3232 S 1.9 1.4 0:00.04 apache2
9906 www-data 20 0 69232 7256 3232 S 1.9 1.4 0:00.04 apache2
9908 www-data 20 0 69232 7256 3232 S 1.9 1.4 0:00.06 apache2
1 root 20 0 2836 760 460 S 0.0 0.1 0:01.50 init
2 root 20 0 0 0 0 S 0.0 0.0 0:00.01 kthreadd
3 root 20 0 0 0 0 S 0.0 0.0 0:00.99 ksoftirqd/0
4 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0
5 root RT 0 0 0 0 S 0.0 0.0 0:00.00 watchdog/0
6 root 20 0 0 0 0 S 0.0 0.0 0:04.20 events/0
7 root 20 0 0 0 0 S 0.0 0.0 0:00.00 cpuset
8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 khelper
9 root 20 0 0 0 0 S 0.0 0.0 0:00.00 netns
10 root 20 0 0 0 0 S 0.0 0.0 0:00.00 async/mgr
11 root 20 0 0 0 0 S 0.0 0.0 0:00.00 pm
12 root 20 0 0 0 0 S 0.0 0.0 0:00.45 sync_supers
13 root 20 0 0 0 0 S 0.0 0.0 0:00.62 bdi-default
14 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kintegrityd/0
15 root 20 0 0 0 0 S 0.0 0.0 0:05.89 kblockd/0
16 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpid
17 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpi_notify
18 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpi_hotplug
19 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ata_aux
20 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ata_sff/0
21 root 20 0 0 0 0 S 0.0 0.0 0:00.00 khubd
22 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kseriod
23 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kmmcd
25 root 20 0 0 0 0 S 0.0 0.0 0:00.08 khungtaskd
26 root 20 0 0 0 0 S 0.0 0.0 0:08.30 kswapd0
27 root 25 5 0 0 0 S 0.0 0.0 0:00.00 ksmd
28 root 20 0 0 0 0 S 0.0 0.0 0:00.00 aio/0
29 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ecryptfs-kthrea
30 root 20 0 0 0 0 S 0.0 0.0 0:00.00 crypto/0
35 root 20 0 0 0 0 S 0.0 0.0 0:00.00 pciehpd
37 root 20 0 0 0 0 S 0.0 0.0 0:00.00 scsi_eh_0
38 root 20 0 0 0 0 S 0.0 0.0 0:00.02 scsi_eh_1
41 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kstriped
42 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kmpathd/0
43 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kmpath_handlerd
44 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ksnapd
45 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kondemand/0
46 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kconservative/0
239 root 20 0 0 0 0 S 0.0 0.0 0:03.95 mpt_poll_0
240 root 20 0 0 0 0 S 0.0 0.0 0:00.00 mpt/0
241 root 20 0 0 0 0 S 0.0 0.0 0:00.00 scsi_eh_2
258 root 20 0 0 0 0 S 0.0 0.0 0:05.60 jbd2/sda1-8
259 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ext4-dio-unwrit
304 root 20 0 2392 68 68 S 0.0 0.0 0:00.04 upstart-udev-br
306 root 16 -4 2440 72 68 S 0.0 0.0 0:00.06 udevd
414 root 18 -2 2328 64 60 S 0.0 0.0 0:00.00 udevd
415 root 18 -2 2328 64 60 S 0.0 0.0 0:00.00 udevd
518 root 20 0 0 0 0 S 0.0 0.0 0:02.87 vmmemctl
526 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kpsmoused
556 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kgameportd
618 syslog 20 0 33976 440 440 S 0.0 0.1 0:00.83 rsyslogd
689 root 20 0 1856 84 80 S 0.0 0.0 0:00.00 getty
693 root 20 0 1856 84 80 S 0.0 0.0 0:00.00 getty
697 root 20 0 1856 84 80 S 0.0 0.0 0:00.00 getty
698 root 20 0 1856 84 80 S 0.0 0.0 0:00.00 getty
701 root 20 0 1856 84 80 S 0.0 0.0 0:00.00 getty
703 memcache 20 0 54192 128 128 S 0.0 0.0 0:07.77 memcached
705 root 20 0 2456 268 204 S 0.0 0.1 0:00.42 cron
706 daemon 20 0 2316 0 0 S 0.0 0.0 0:00.00 atd
722 root 20 0 5640 360 256 S 0.0 0.1 0:00.53 sshd
753 mysql 20 0 153m 456 32 S 0.0 0.1 0:20.57 mysqld
9280 root 20 0 2780 1408 1064 S 0.0 0.3 0:00.05 login
9292 zim32 20 0 8828 6068 1536 S 0.0 1.2 0:00.26 bash
9324 root 20 0 7268 2968 2180 S 0.0 0.6 0:03.50 mc
9326 root 20 0 6252 3544 1588 S 0.0 0.7 0:00.21 bash
9735 root 20 0 0 0 0 S 0.0 0.0 0:00.00 flush-8:0
9808 root 20 0 68892 8624 4828 S 0.0 1.7 0:00.15 apache2
9814 www-data 20 0 69232 7260 3232 S 0.0 1.4 0:01.03 apache2
9827 www-data 20 0 69232 7260 3232 S 0.0 1.4 0:00.97 apache2
9842 www-data 20 0 69232 7264 3236 S 0.0 1.4 0:00.40 apache2
9844 www-data 20 0 69232 7260 3232 S 0.0 1.4 0:00.40 apache2
9870 www-data 20 0 69232 7264 3236 S 0.0 1.4 0:00.22 apache2
9872 www-data 20 0 69232 7260 3232 S 0.0 1.4 0:00.23 apache2
9877 www-data 20 0 69232 7260 3232 S 0.0 1.4 0:00.18 apache2
9878 www-data 20 0 69232 7260 3232 S 0.0 1.4 0:00.18 apache2
9888 www-data 20 0 69232 7260 3232 S 0.0 1.4 0:00.07 apache2
9889 www-data 20 0 69232 7260 3232 S 0.0 1.4 0:00.06 apache2
9891 www-data 20 0 69232 7260 3232 S 0.0 1.4 0:00.08 apache2
9892 www-data 20 0 69232 7256 3232 S 0.0 1.4 0:00.05 apache2
9893 www-data 20 0 69232 7260 3232 S 0.0 1.4 0:00.06 apache2
9894 www-data 20 0 69232 7256 3232 S 0.0 1.4 0:00.08 apache2
9895 www-data 20 0 69232 7256 3232 S 0.0 1.4 0:00.06 apache2
9896 www-data 20 0 69232 7256 3232 S 0.0 1.4 0:00.04 apache2
9897 www-data 20 0 69232 7248 3228 S 0.0 1.4 0:00.06 apache2
9898 www-data 20 0 69232 7260 3232 S 0.0 1.4 0:00.03 apache2
9899 www-data 20 0 69232 7260 3236 S 0.0 1.4 0:00.06 apache2
9901 www-data 20 0 69232 7260 3232 S 0.0 1.4 0:00.04 apache2
9902 www-data 20 0 69232 7256 3232 S 0.0 1.4 0:00.04 apache2
9903 www-data 20 0 69232 7260 3232 S 0.0 1.4 0:00.03 apache2
9904 www-data 20 0 69232 7256 3232 S 0.0 1.4 0:00.08 apache2
9905 www-data 20 0 69232 7256 3232 S 0.0 1.4 0:00.05 apache2
9907 www-data 20 0 69232 7260 3232 S 0.0 1.4 0:00.05 apache2
9909 www-data 20 0 69232 7256 3232 S 0.0 1.4 0:00.08 apache2
9911 www-data 20 0 69232 7256 3232 S 0.0 1.4 0:00.04 apache2
9912 www-data 20 0 69232 7248 3228 S 0.0 1.4 0:00.04 apache2
9913 www-data 20 0 69232 7260 3232 S 0.0 1.4 0:00.06 apache2
9914 www-data 20 0 69232 7260 3232 S 0.0 1.4 0:00.04 apache2
9915 www-data 20 0 69232 7260 3232 R 0.0 1.4 0:00.04 apache2
9916 www-data 20 0 69232 7256 3232 S 0.0 1.4 0:00.04 apache2
9917 www-data 20 0 69232 7256 3232 S 0.0 1.4 0:00.06 apache2
9918 www-data 20 0 69232 7248 3228 S 0.0 1.4 0:00.02 apache2
9919 root 20 0 2632 1068 816 R 0.0 0.2 0:00.02 top