主要通过以下的几个jvm参数来设置堆内存的：
-Xmx512m     最大总堆内存，一般设置为物理内存的1/4
-Xms512m     初始总堆内存，一般将它设置的和最大堆内存一样大，这样就不需要根据当前堆使用情况而调整堆的大小了
-Xmn192m     年轻带堆内存，sun官方推荐为整个堆的3/8
堆内存的组成     总堆内存 = 年轻带堆内存 + 年老带堆内存 + 持久带堆内存
年轻带堆内存     对象刚创建出来时放在这里
年老带堆内存     对象在被真正会回收之前会先放在这里
持久带堆内存     class文件，元数据等放在这里
-XX:PermSize=128m     持久带堆的初始大小
-XX:MaxPermSize=128m     持久带堆的最大大小，eclipse默认为256m。如果要编译jdk这种，一定要把这个设的很大，因为它的类太多了。

-Xms5200M -Xmx5200M -XX:PermSize=512M -XX:MaxPermSize=512M

C:\Users\liqia>jps
520404 Bootstrap
575844 Jps
348088

C:\Users\liqia>jmap -heap 520404
Attaching to process ID 520404, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.80-b11using thread-local object allocation.
Parallel GC with 4 thread(s)Heap Configuration:MinHeapFreeRatio = 0MaxHeapFreeRatio = 100MaxHeapSize      = 5452595200 (5200.0MB)NewSize          = 1310720 (1.25MB)MaxNewSize       = 17592186044415 MBOldSize          = 5439488 (5.1875MB)NewRatio         = 2SurvivorRatio    = 8PermSize         = 536870912 (512.0MB)MaxPermSize      = 536870912 (512.0MB)G1HeapRegionSize = 0 (0.0MB)Heap Usage:
PS Young Generation
Eden Space:capacity = 1363673088 (1300.5MB)used     = 1122021344 (1070.0429382324219MB)free     = 241651744 (230.45706176757812MB)82.27934934505359% used
From Space:capacity = 227016704 (216.5MB)used     = 172383432 (164.39765167236328MB)free     = 54633272 (52.10234832763672MB)75.93425019508696% used
To Space:capacity = 227016704 (216.5MB)used     = 0 (0.0MB)free     = 227016704 (216.5MB)0.0% used
PS Old Generationcapacity = 3635412992 (3467.0MB)used     = 73744 (0.0703277587890625MB)free     = 3635339248 (3466.929672241211MB)0.0020284903025400204% used
PS Perm Generationcapacity = 536870912 (512.0MB)used     = 58398232 (55.692893981933594MB)free     = 478472680 (456.3071060180664MB)10.877518355846405% used

-startup
plugins/org.eclipse.equinox.launcher_1.3.100.v20150511-1540.jar
--launcher.library
plugins/org.eclipse.equinox.launcher.win32.win32.x86_64_1.1.300.v20150602-1417
-product
org.eclipse.epp.package.jee.product
--launcher.defaultAction
openFile
--launcher.XXMaxPermSize
1024M
-showsplash
org.eclipse.platform
--launcher.XXMaxPermSize
1024m
--launcher.defaultAction
openFile
--launcher.appendVmargs
-vmargs
-Dosgi.requiredJavaVersion=1.7
-Xms4096m
-Xmx4096m
-XX:PermSize=512m
-XX:MaxPermSize=512m
-Xloggc:gc.log
-XX:+PrintGCTimeStamps
-XX:+PrintGCDetails

C:\Users\liqia>jmap -heap 348088
Attaching to process ID 348088, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.80-b11using thread-local object allocation.
Parallel GC with 4 thread(s)Heap Configuration:MinHeapFreeRatio = 0MaxHeapFreeRatio = 100MaxHeapSize      = 4294967296 (4096.0MB)NewSize          = 1310720 (1.25MB)MaxNewSize       = 17592186044415 MBOldSize          = 5439488 (5.1875MB)NewRatio         = 2SurvivorRatio    = 8PermSize         = 536870912 (512.0MB)MaxPermSize      = 536870912 (512.0MB)G1HeapRegionSize = 0 (0.0MB)Heap Usage:
PS Young Generation
Eden Space:capacity = 1145569280 (1092.5MB)used     = 202738320 (193.34632873535156MB)free     = 942830960 (899.1536712646484MB)17.697604460901744% used
From Space:capacity = 146800640 (140.0MB)used     = 46552800 (44.396209716796875MB)free     = 100247840 (95.60379028320312MB)31.711578369140625% used
To Space:capacity = 139460608 (133.0MB)used     = 0 (0.0MB)free     = 139460608 (133.0MB)0.0% used
PS Old Generationcapacity = 2863661056 (2731.0MB)used     = 154200136 (147.05670928955078MB)free     = 2709460920 (2583.943290710449MB)5.384720222978791% used
PS Perm Generationcapacity = 536870912 (512.0MB)used     = 153296424 (146.19486236572266MB)free     = 383574488 (365.80513763427734MB)28.553684055805206% used