everybody,the memory usage is too much,what can i do?

top - 12:54:37 up 7 days, 4:38, 1 user, load average: 0.00, 0.00, 0.00 Tasks: 18 total, 2 running, 16 sleeping, 0 stopped, 0 zombie Cpu(s): 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 1048800k total, 917424k used, 131376k free, 0k buffers Swap: 0k total, 0k used, 0k free, 0k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND

1 root 15 0 2840 1364 1204 S 0.0 0.1 0:02.17 init

1161 root 14 -4 2320 600 420 S 0.0 0.1 0:00.00 udevd

1391 root 18 0 35512 1288 948 S 0.0 0.1 0:03.53 rsyslogd

1409 root 15 0 8432 1164 700 S 0.0 0.1 0:03.87 sshd

1416 root 18 0 3156 868 692 S 0.0 0.1 0:00.00 xinetd

1423 root 18 0 8672 716 292 S 0.0 0.1 0:00.00 saslauthd

1424 root 18 0 8672 488 64 S 0.0 0.0 0:00.00 saslauthd

1431 root 15 0 7020 1168 616 S 0.0 0.1 0:00.99 crond

1450 root 25 0 6236 1444 1228 S 0.0 0.1 0:00.05 sh

3328 mysql 15 0 799m 42m 4892 S 0.0 4.1 0:02.07 mysqld

15479 root 15 0 11304 3332 2688 R 0.0 0.3 0:00.06 sshd

15482 root 15 0 6372 1688 1404 S 0.0 0.2 0:00.00 bash

15497 root 15 0 2536 1044 864 R 0.0 0.1 0:00.00 top

20137 www 15 0 20672 14m 864 S 0.0 1.4 0:00.87 nginx

22351 www 16 0 52324 26m 9244 S 0.0 2.6 0:13.94 php-fpm

24231 www 16 0 51928 25m 9260 S 0.0 2.5 0:13.52 php-fpm

32682 root 15 0 35832 3228 864 S 0.0 0.3 0:02.18 php-fpm

32686 root 18 0 7368 1616 888 S 0.0 0.2 0:00.00 nginx