在劉冬的文章“
Java虛擬機的最大內存是多少 ”一文中
今天分析了當前比較流行的幾個不同公司不同版本JVM的最大內存，得出來的結果如下：
公司 JVM版本 最大內存(兆)client 最大內存(兆)server
SUN 1.5.x 1492 1520
SUN 1.5.5(Linux) 2634 2660
SUN 1.4.2 1564 1564
SUN 1.4.2(Linux) 1900 1260
IBM 1.4.2(Linux) 2047 N/A
BEA JRockit 1.5 (U3) 1909 1902
除非特別說明，否則JVM版本都運行在Windows操作系統下
附：如何獲得JVM的最大可用內存
在命令行下用 java -XmxXXXXM -version 命令來進行測試，然后逐漸的增大XXXX的值，如果執行正常就表示指定的內存大小可用，否則會打印錯誤信息。
實際發現版本上有細微差別的JDK最大容許內存值都不盡相同，因此在實際的應用中還是要自己試驗一下看到底內存能達到什么樣的值。
通過這個表想說明的是，如果你的機器的內存太多的話，只能通過多運行幾個實例來提供機器的利用率了，例如跑Tomcat，你可以多裝幾個Tomcat并做集群，依此類推。我在新到的一臺dell 2850服務器上做測試
1、使用sun jdk1.4.2_07,測試結果為
[root@localhost bin]# ./java -Xmx3710M -version
Error occurred during initialization of VM
Could not reserve enough space for object heap
[root@localhost bin]# ./java -Xmx3700M -version
java version "1.4.2_07"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_07-b05)
Java HotSpot(TM) Client VM (build 1.4.2_07-b05, mixed mode) 2、使用sun jdk 1.5.6,測試結果為
[root@localhost bin]# ./java -Xmx3700M -version
Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.
[root@localhost bin]# ./java -Xmx3600M -version
java version "1.5.0_06"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_06-b05)
Java HotSpot(TM) Server VM (build 1.5.0_06-b05, mixed mode) 服務器的配置情況
[root@localhost bin]# top
top - 14:32:23 up 5 days, 21:06, 3 users, load average: 0.00, 0.03, 0.00
Tasks: 114 total, 1 running, 113 sleeping, 0 stopped, 0 zombie
Cpu0 : 0.0% us, 0.0% sy, 0.0% ni, 100.0% id, 0.0% wa, 0.0% hi, 0.0% si
Cpu1 : 0.0% us, 0.0% sy, 0.0% ni, 100.0% id, 0.0% wa, 0.0% hi, 0.0% si
Cpu2 : 2.3% us, 0.0% sy, 0.0% ni, 97.7% id, 0.0% wa, 0.0% hi, 0.0% si
Cpu3 : 0.3% us, 0.0% sy, 0.0% ni, 99.7% id, 0.0% wa, 0.0% hi, 0.0% si
Mem: 4044816k total, 1810908k used, 2233908k free, 92088k buffers
Swap: 2555888k total, 0k used, 2555888k free, 1333328k cached
[root@localhost bin]# cat /proc/meminfo
MemTotal: 4044816 kB
MemFree: 2234092 kB
Buffers: 92088 kB
Cached: 1333328 kB
SwapCached: 0 kB
Active: 671408 kB
Inactive: 939560 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 4044816 kB
LowFree: 2234092 kB
SwapTotal: 2555888 kB
SwapFree: 2555888 kB
Dirty: 0 kB
Writeback: 0 kB
Mapped: 230684 kB
Slab: 148664 kB
Committed_AS: 642520 kB
PageTables: 6332 kB
VmallocTotal: 536870911 kB
VmallocUsed: 264596 kB
VmallocChunk: 536606195 kB
HugePages_Total: 0
HugePages_Free: 0
Hugepagesize: 2048 kB
[root@localhost bin]# cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 15
model : 4
model name : Intel(R) Xeon(TM) CPU 3.00GHz
stepping : 3
cpu MHz : 2992.789
cache size : 2048 KB
physical id : 0
siblings : 2
fpu : yes
fpu_exception : yes
cpuid level : 5
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm pni monitor ds_cpl cid cx16 xtpr
bogomips : 5931.00
clflush size : 64
cache_alignment : 128
address sizes : 36 bits physical, 48 bits virtual
power management:
processor : 1
vendor_id : GenuineIntel
cpu family : 15
model : 4
model name : Intel(R) Xeon(TM) CPU 3.00GHz
stepping : 3
cpu MHz : 2992.789
cache size : 2048 KB
physical id : 3
siblings : 2
fpu : yes
fpu_exception : yes
cpuid level : 5
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm pni monitor ds_cpl cid cx16 xtpr
bogomips : 5980.16
clflush size : 64
cache_alignment : 128
address sizes : 36 bits physical, 48 bits virtual
power management:
processor : 2
vendor_id : GenuineIntel
cpu family : 15
model : 4
model name : Intel(R) Xeon(TM) CPU 3.00GHz
stepping : 3
cpu MHz : 2992.789
cache size : 2048 KB
physical id : 0
siblings : 2
fpu : yes
fpu_exception : yes
cpuid level : 5
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm pni monitor ds_cpl cid cx16 xtpr
bogomips : 5980.16
clflush size : 64
cache_alignment : 128
address sizes : 36 bits physical, 48 bits virtual
power management:
processor : 3
vendor_id : GenuineIntel
cpu family : 15
model : 4
model name : Intel(R) Xeon(TM) CPU 3.00GHz
stepping : 3
cpu MHz : 2992.789
cache size : 2048 KB
physical id : 3
siblings : 2
fpu : yes
fpu_exception : yes
cpuid level : 5
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm pni monitor ds_cpl cid cx16 xtpr
bogomips : 5980.16
clflush size : 64
cache_alignment : 128
address sizes : 36 bits physical, 48 bits virtual
power management: