我有一个带4GB RAM的ubuntu 14.04系统,x86_64 3.13.0-48通用内核和openjdk-7.

我的记忆用法如下：

# free -h
             total       used       free     shared    buffers     cached
Mem:          3.7G       3.6G       127M       988M        44M       3.3G
-/+ buffers/cache:       232M       3.4G
Swap:           0B         0B         0B

因此,有足够的内存用作磁盘缓存,当任何应用程序需要时,应该刷新和释放(AFAIK).

所以,我尝试运行java：

# java -Xms32m -Xmx512m -version
Error occurred during initialization of VM
Could not reserve enough space for object heap
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

只运行java -version会返回相同的结果.当有3GB的缓存内存时,为什么java不能运行？我在同一台机器上运行Postresql,但它的shared_buffers设置为940MB.

编辑：

我强制刷新磁盘缓存 – 仍然是相同的结果：

# free -h
             total       used       free     shared    buffers     cached
Mem:          3.7G       1.9G       1.8G       988M        35M       1.7G
-/+ buffers/cache:       196M       3.5G
Swap:           0B         0B         0B
# java -Xms32m -Xmx512m -version
Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.

EDIT2：

这是ulimit -a：

# ulimit -a
core file size          (blocks,-c) 0
data seg size           (kbytes,-d) unlimited
scheduling priority             (-e) 0
file size               (blocks,-f) unlimited
pending signals                 (-i) 30034
max locked memory       (kbytes,-l) 64
max memory size         (kbytes,-m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes,-p) 8
POSIX message queues     (bytes,-q) 819200
real-time priority              (-r) 0
stack size              (kbytes,-s) 32000
cpu time               (seconds,-t) unlimited
max user processes              (-u) 30034
virtual memory          (kbytes,-v) unlimited
file locks                      (-x) unlimited

EDIT3：

我完全没有得到它：我试图添加4GB交换,结果是它工作,虽然没有使用交换：

# free -h
             total       used       free     shared    buffers     cached
Mem:          3.7G       3.5G       196M       988M        44M       3.2G
-/+ buffers/cache:       239M       3.4G
Swap:         4.0G         0B       4.0G
# java -version
java version "1.6.0_36"
OpenJDK Runtime Environment (IcedTea6 1.13.8) (6b36-1.13.8-0ubuntu1~14.04)
OpenJDK 64-Bit Server VM (build 23.25-b01,mixed mode)