如果没有任何进程使用内存，那么我的内存几乎已经满了。
也许您认为这是一个重复的问题，但与其他问题不同，它-/+ buffers/cache也被使用。这是相关命令的输出：
top - 00:27:38 up 2 days, 21:54, 1 user, load average: 0.07, 0.05, 0.05
Tasks: 90 total, 1 running, 89 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.3%us, 0.0%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 1020116k total, 882460k used, 137656k free, 11868k buffers
Swap: 2064380k total, 22528k used, 2041852k free, 137824k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
15249 root 20 0 15024 1284 984 R 0.3 0.1 0:00.04 top
1 root 20 0 19360 712 500 S 0.0 0.1 0:06.88 init
2 root 20 0 0 0 0 S 0.0 0.0 0:00.04 kthreadd
3 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0
4 root 20 0 0 0 0 S 0.0 0.0 0:01.85 ksoftirqd/0
5 root RT 0 0 0 0 S 0.0 0.0 0:00.00 stopper/0
6 root RT 0 0 0 0 S 0.0 0.0 0:01.19 watchdog/0
7 root 20 0 0 0 0 S 0.0 0.0 0:18.39 events/0
8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 events/0
9 root 20 0 0 0 0 S 0.0 0.0 0:00.00 events_long/0
10 root 20 0 0 0 0 S 0.0 0.0 0:00.00 events_power_ef
11 root 20 0 0 0 0 S 0.0 0.0 0:00.00 cgroup
12 root 20 0 0 0 0 S 0.0 0.0 0:00.00 khelper
13 root 20 0 0 0 0 S 0.0 0.0 0:00.00 netns
14 root 20 0 0 0 0 S 0.0 0.0 0:00.00 async/mgr
15 root 20 0 0 0 0 S 0.0 0.0 0:00.00 pm
16 root 20 0 0 0 0 S 0.0 0.0 0:00.76 sync_supers
17 root 20 0 0 0 0 S 0.0 0.0 0:00.62 bdi-default
18 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kintegrityd/0
19 root 20 0 0 0 0 S 0.0 0.0 0:01.59 kblockd/0
20 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpid
21 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpi_notify
22 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpi_hotplug
23 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ata_aux
24 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ata_sff/0
25 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ksuspend_usbd
26 root 20 0 0 0 0 S 0.0 0.0 0:00.00 khubd
27 root 20 0 0 0 0 S 0.0 0.0 0:00.02 kseriod
28 root 20 0 0 0 0 S 0.0 0.0 0:00.00 md/0
29 root 20 0 0 0 0 S 0.0 0.0 0:00.00 md_misc/0
30 root 20 0 0 0 0 S 0.0 0.0 0:00.00 linkwatch
32 root 20 0 0 0 0 S 0.0 0.0 0:00.06 khungtaskd
33 root 20 0 0 0 0 S 0.0 0.0 0:24.98 kswapd0
34 root 25 5 0 0 0 S 0.0 0.0 0:00.00 ksmd
35 root 39 19 0 0 0 S 0.0 0.0 0:09.29 khugepaged
36 root 20 0 0 0 0 S 0.0 0.0 0:00.00 aio/0
37 root 20 0 0 0 0 S 0.0 0.0 0:00.00 crypto/0
44 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthrotld/0
45 root 20 0 0 0 0 S 0.0 0.0 0:00.00 pciehpd
47 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kpsmoused
48 root 20 0 0 0 0 S 0.0 0.0 0:00.00 usbhid_resumer
49 root 20 0 0 0 0 S 0.0 0.0 0:00.00 deferwq
82 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kdmremove
83 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kstriped
和
# free -m:
total used free shared buffers cached
Mem: 996 861 134 0 11 134
-/+ buffers/cache: 715 280
Swap: 2015 22 1993
和
root@reverser ~]# ps_mem
Private + Shared = RAM used Program
4.0 KiB + 31.5 KiB = 35.5 KiB dbus-daemon
4.0 KiB + 56.5 KiB = 60.5 KiB vsftpd
84.0 KiB + 28.0 KiB = 112.0 KiB anvil
36.0 KiB + 86.5 KiB = 122.5 KiB udevd (3)
24.0 KiB + 99.0 KiB = 123.0 KiB mingetty (6)
116.0 KiB + 31.5 KiB = 147.5 KiB dovecot
128.0 KiB + 29.0 KiB = 157.0 KiB log
132.0 KiB + 39.0 KiB = 171.0 KiB crond
124.0 KiB + 104.0 KiB = 228.0 KiB exim
224.0 KiB + 37.0 KiB = 261.0 KiB auditd
324.0 KiB + 45.0 KiB = 369.0 KiB init
392.0 KiB + 205.0 KiB = 597.0 KiB fail2ban-server
716.0 KiB + 48.5 KiB = 764.5 KiB rsyslogd
452.0 KiB + 353.0 KiB = 805.0 KiB nginx (4)
968.0 KiB + 84.0 KiB = 1.0 MiB bash
1.5 MiB + 313.0 KiB = 1.8 MiB sshd (2)
1.7 MiB + 395.5 KiB = 2.1 MiB vesta-nginx (2)
2.1 MiB + 1.8 MiB = 3.9 MiB vesta-php (3)
7.5 MiB + 91.0 KiB = 7.6 MiB named
---------------------------------
20.3 MiB
=================================
我应该怎么做才能减少内存使用量？