java memory allocation under linux
- by pstanton
I'm running 4 java processes with the following command:
java -Xmx256m -jar ...
and the system has 8Gb memory under fedora 12.
however it is apparently going into swap.
how can that be if 4 x 256m = 1Gb ?
EDIT: also, how can all 8Gb of memory be used with so little memory allocated to basically the only thing running?
is it java not garbage collecting because the OS tells it it doesn't need to or what?
TOP:
top - 20:13:57 up 3:55, 6 users, load average: 1.99, 2.54, 2.67
Tasks: 251 total, 6 running, 245 sleeping, 0 stopped, 0 zombie
Cpu(s): 50.1%us, 2.9%sy, 0.0%ni, 45.1%id, 1.1%wa, 0.0%hi, 0.8%si, 0.0%st
Mem: 8252304k total, 8195552k used, 56752k free, 34356k buffers
Swap: 10354680k total, 74044k used, 10280636k free, 6624148k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1948 xxxxxxxx 20 0 1624m 240m 4020 S 96.8 3.0 164:33.75 java
1927 xxxxxxxx 20 0 139m 31m 27m R 91.8 0.4 38:34.55 postgres
1929 xxxxxxxx 20 0 1624m 200m 3984 S 86.2 2.5 183:24.88 java
1969 xxxxxxxx 20 0 1624m 292m 3984 S 65.6 3.6 154:06.76 java
1987 xxxxxxxx 20 0 137m 29m 27m R 28.5 0.4 75:49.82 postgres
1581 root 20 0 159m 18m 4712 S 22.5 0.2 52:42.54 Xorg
2411 xxxxxxxx 20 0 309m 9748 4544 S 20.9 0.1 45:05.08 gnome-system-mo
1947 xxxxxxxx 20 0 137m 28m 27m S 13.3 0.4 44:46.04 postgres
1772 xxxxxxxx 20 0 135m 25m 25m S 4.0 0.3 1:09.14 postgres
1966 xxxxxxxx 20 0 137m 29m 27m S 3.0 0.4 64:27.09 postgres
1773 xxxxxxxx 20 0 135m 732 624 S 1.0 0.0 0:24.86 postgres
2464 xxxxxxxx 20 0 15028 1156 744 R 0.7 0.0 0:49.14 top
344 root 15 -5 0 0 0 S 0.3 0.0 0:02.26 kdmflush
1 root 20 0 4124 620 524 S 0.0 0.0 0:00.88 init
2 root 15 -5 0 0 0 S 0.0 0.0 0:00.00 kthreadd
3 root RT -5 0 0 0 S 0.0 0.0 0:00.00 migration/0
4 root 15 -5 0 0 0 S 0.0 0.0 0:00.04 ksoftirqd/0
