redhat 6.5启用named服务，内存使用越来越多，求解

top信息如下：
top - 17:06:27 up 5 days, 17:31, 2 users, load average: 1.29, 1.42, 1.34
Tasks: 265 total, 3 running, 261 sleeping, 0 stopped, 1 zombie
Cpu(s): 9.5%us, 18.9%sy, 5.5%ni, 64.5%id, 1.0%wa, 0.0%hi, 0.5%si, 0.0%st
Mem: 16335664k total, 6394636k used, 9941028k free, 3196k buffers
Swap: 8290296k total, 0k used, 8290296k free, 3933100k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1659 named 20 0 1407m 1.0g 3116 S 66.1 6.7 3129:56 named
1869 root 20 0 372m 339m 800 S 23.3 2.1 20:19.88 dbus-daemon
12738 root 30 10 377m 83m 6920 S 23.3 0.5 0:01.77 sosreport
1619 dbus 20 0 32580 2020 872 R 8.4 0.0 13:05.75 dbus-daemon
1997 root 20 0 45372 2788 2180 S 6.5 0.0 9:28.70 udisks-daemon
3 root RT 0 0 0 0 S 1.6 0.0 0:04.82 migration/0
9803 root 20 0 15168 1368 932 R 1.3 0.0 0:00.66 top
1860 root 20 0 249m 6784 5392 S 1.0 0.0 1:21.02 gnome-session
2028 root 20 0 312m 11m 8492 S 1.0 0.1 1:05.25 nm-applet
2097 root 20 0 460m 11m 8680 S 1.0 0.1 1:24.87 gpk-update-icon
12919 root 20 0 0 0 0 R 1.0 0.0 0:00.03 dbus-daemon
12920 root 20 0 145m 3352 2784 S 1.0 0.0 0:00.03 gvfs-gdu-volume
23 root RT 0 0 0 0 S 0.6 0.0 0:04.49 migration/5
1442 root 20 0 243m 5412 1088 S 0.6 0.0 15:24.87 rsyslogd
1942 root 20 0 289m 8312 6280 S 0.6 0.1 0:41.98 seahorse-daemon
1954 root 18 -2 11220 1568 552 S 0.6 0.0 0:01.16 udevd
2019 root 20 0 255m 8268 5880 S 0.6 0.1 0:54.99 gnome-power-man
2304 root 20 0 40964 2232 1920 S 0.6 0.0 0:28.01 gconf-im-settin
1 root 20 0 19356 1532 1224 S 0.3 0.0 0:16.38 init
4 root 20 0 0 0 0 S 0.3 0.0 0:28.64 ksoftirqd/0
29 root 20 0 0 0 0 S 0.3 0.0 0:20.78 ksoftirqd/6
543 root 16 -4 11220 1320 320 S 0.3 0.0 0:01.46 udevd
1467 root 20 0 0 0 0 S 0.3 0.0 3:08.49 kondemand/2
1471 root 20 0 0 0 0 S 0.3 0.0 3:14.30 kondemand/6
1472 root 20 0 0 0 0 S 0.3 0.0 3:01.26 kondemand/7
1749 haldaemo 20 0 38888 5264 4308 S 0.3 0.0 0:18.33 hald
1948 root 20 0 136m 2224 1904 S 0.3 0.0 0:36.74 gvfsd
1974 root 20 0 549m 214m 10m S 0.3 1.3 0:39.19 gnome-panel
1975 root 20 0 885m 93m 14m S 0.3 0.6 0:32.29 nautilus
1981 root 20 0 133m 2284 1960 S 0.3 0.0 0:16.14 gdm-binary
2020 root 20 0 168m 35m 7132 S 0.3 0.2 2:13.57 Xorg
2024 root 20 0 257m 8556 6484 S 0.3 0.1 0:20.27 bluetooth-apple
2030 root 20 0 122m 4000 3328 S 0.3 0.0 0:34.34 im-settings-dae
2034 root 20 0 4020m 3544 2112 S 0.3 0.0 0:18.42 console-kit-dae
2100 root 20 0 252m 7124 5696 S 0.3 0.0 0:00.44 gdu-notificatio
2110 root 20 0 49864 2708 2112 S 0.3 0.0 0:16.37 devkit-power-da
2150 root 20 0 52616 4192 2984 S 0.3 0.0 0:40.23 polkitd
4729 root 18 -2 11220 1568 552 S 0.3 0.0 0:00.38 udevd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.03 kthreadd
5 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0
6 root RT 0 0 0 0 S 0.0 0.0 0:00.45 watchdog/0
7 root RT 0 0 0 0 S 0.0 0.0 0:04.99 migration/1
8 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/1
9 root 20 0 0 0 0 S 0.0 0.0 0:22.84 ksoftirqd/1
10 root RT 0 0 0 0 S 0.0 0.0 0:00.29 watchdog/1
11 root RT 0 0 0 0 S 0.0 0.0 0:04.69 migration/2
12 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/2
13 root 20 0 0 0 0 S 0.0 0.0 0:22.69 ksoftirqd/2
14 root RT 0 0 0 0 S 0.0 0.0 0:00.20 watchdog/2
15 root RT 0 0 0 0 S 0.0 0.0 0:05.52 migration/3