SystemInfo
操作系统：archlinux
JDK:OpenJDK（IcedTea 2.4.3）（ArchLinux版本7.u45_2.4.3-1-x86_64）
正在运行的应用程序：https://github.com/aemoncannon/ensime
我的java选项：
-Xms128m -Xmx512M -Xss1M -XX:MaxPermSize=50m
-XX:MaxDirectMemorySize=10M
-XX:ReservedCodeCacheSize=64m
-Dfile.encoding=UTF-8 -XX:NativeMemoryTracking=detai
Linux top命令显示，它使用6.8G*19.5%=1.326GB
Natvie内存跟踪显示它使用713MB
所以。哪一个是实际的物理内存使用量，如果它使用1.3GB内存，额外的600多MB物理内存放在哪里？
顶部输出
top - 09:20:37 up 48 min, 2 users, load average: 0.31, 0.33, 0.36
Tasks: 161 total, 1 running, 159 sleeping, 0 stopped, 1 zombie
%Cpu(s): 0.7 us, 0.3 sy, 0.0 ni, 99.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0
KiB Mem: 7091684 total, 4338428 used, 2753256 free, 117044 buffers
KiB Swap: 8388604 total, 0 used, 8388604 free, 1399904 cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
5666 jilen 20 0 3553516 1.317g 22652 S 0.3 19.5 2:27.72 java
本机内存跟踪输出（jcmd VM.native_memory detail）
Native Memory Tracking:
Total: reserved=731125KB, committed=681117KB
- Java Heap (reserved=575488KB, committed=574976KB)
(mmap: reserved=575488KB, committed=574976KB)
- Class (reserved=6388KB, committed=6388KB)
(classes #6443)
(malloc=6388KB, #16725)
- Thread (reserved=27986KB, committed=27986KB)
(thread #27)
(stack: reserved=27756KB, committed=27756KB)
(malloc=82KB, #114)
(arena=148KB, #54)
- Code (reserved=70523KB, committed=21059KB)
(malloc=3963KB, #6149)
(mmap: reserved=66560KB, committed=17096KB)
- GC (reserved=26964KB, committed=26964KB)
(malloc=5900KB, #158)
(mmap: reserved=21064KB, committed=21064KB)
- Compiler (reserved=176KB, committed=176KB)
(malloc=78KB, #238)
(arena=98KB, #2)
- Internal (reserved=5463KB, committed=5431KB)
(malloc=5431KB, #1492)
(mmap: reserved=32KB, committed=0KB)
- Symbol (reserved=10668KB, committed=10668KB)
(malloc=9765KB, #77949)
(arena=903KB, #1)
- Memory Tracking (reserved=5616KB, committed=5616KB)
(malloc=5616KB, #120)
- Pooled Free Chunks (reserved=1854KB, committed=1854KB)
(malloc=1854KB)
Virtual memory map:
[0x00000000dce00000 - 0x0000000100000000] reserved 575488KB for Java Heap
from [JVM_handle_linux_signal+0x173dbd]
[0x00000000dce00000 - 0x00000000fff80000] committed 574976KB from [JVM_handle_linux_signal+0x650ab]
[0x00007f53801c7000 - 0x00007f53802c8000] reserved 1028KB for Thread Stack
from [JVM_handle_linux_signal+0x12f2ec]
[0x00007f53801c7000 - 0x00007f53802c8000] committed 1028KB from [JVM_handle_linux_signal+0x12f2ec]
[0x00007f5381daf000 - 0x00007f5381eb0000] reserved 1028KB for Thread Stack
from [JVM_handle_linux_signal+0x12f2ec]
[0x00007f5381daf000 - 0x00007f5381eb0000] committed 1028KB from [JVM_handle_linux_signal+0x12f2ec]
[0x00007f53821f0000 - 0x00007f53824f3000] reserved 3084KB for Thread Stack
from [JVM_handle_linux_signal+0x12f2ec]
[0x00007f53821f0000 - 0x00007f53824f3000] committed 3084KB from [JVM_handle_linux_signal+0x12f2ec]
[0x00007f5382d49000 - 0x00007f5382e4a000] reserved 1028KB for Thread Stack
from [JVM_handle_linux_signal+0x12f2ec]
[0x00007f5382d49000 - 0x00007f5382e4a000] committed 1028KB from [JVM_handle_linux_signal+0x12f2ec]
[0x00007f538302a000 - 0x00007f538342e000] reserved 4112KB for Thread Stack
from [JVM_handle_linux_signal+0x12f2ec]
[0x00007f538302a000 - 0x00007f538342e000] committed 4112KB from [JVM_handle_linux_signal+0x12f2ec]
[0x00007f53b47c7000 - 0x00007f53b4aca000] reserved 3084KB for Thread Stack
from [JVM_handle_linux_signal+0x12f2ec]
[0x00007f53b47c7000 - 0x00007f53b4aca000] committed 3084KB from [JVM_handle_linux_signal+0x12f2ec]
[0x00007f53b4db7000 - 0x00007f53b4eb8000] reserved 1028KB for Thread Stack
from [JVM_handle_linux_signal+0x127be9]
[0x00007f53b4db7000 - 0x00007f53b4eb8000] committed 1028KB from [JVM_handle_linux_signal+0x127be9]
[0x00007f53b4eb8000 - 0x00007f53b52bc000] reserved 4112KB for Thread Stack
from [JVM_handle_linux_signal+0x12f2ec]
[0x00007f53b4eb8000 - 0x00007f53b52bc000] committed 4112KB from [JVM_handle_linux_signal+0x12f2ec]
[0x00007f53b5894000 - 0x00007f53b5a96000] reserved 2056KB for Thread Stack
from [JVM_handle_linux_signal+0x12f2ec]
[0x00007f53b5894000 - 0x00007f53b5a96000] committed 2056KB from [JVM_handle_linux_signal+0x12f2ec]
[0x00007f53b5a96000 - 0x00007f53b5b97000] reserved 1028KB for Thread Stack
from [JVM_handle_linux_signal+0x17c90d]
[0x00007f53b5a96000 - 0x00007f53b5b97000] committed 1028KB from [JVM_handle_linux_signal+0x17c90d]
[0x00007f53b5b97000 - 0x00007f53b5c98000] reserved 1028KB for Thread Stack
from [JVM_FindSignal+0x118f1b]
[0x00007f53b5b97000 - 0x00007f53b5c98000] committed 1028KB from [JVM_FindSignal+0x118f1b]
[0x00007f53b6e70000 - 0x00007f53b8000000] reserved 17984KB for GC
from [JVM_handle_linux_signal+0x172529]
[0x00007f53b6e70000 - 0x00007f53b8000000] committed 17984KB from [JVM_handle_linux_signal+0x650ab]
[0x00007f53c4000000 - 0x00007f53c8000000] reserved 65536KB for Code
from [JVM_handle_linux_signal+0x1741a5]
[0x00007f53c4000000 - 0x00007f53c5070000] committed 16832KB from [JVM_handle_linux_signal+0x1746f4]
[0x00007f53cc0e4000 - 0x00007f53cc1fd000] reserved 1124KB for GC
from [JVM_handle_linux_signal+0x172529]
[0x00007f53cc0e4000 - 0x00007f53cc1fd000] committed 1124KB from [JVM_handle_linux_signal+0x650ab]
[0x00007f53cc1fd000 - 0x00007f53cc601000] reserved 4112KB for Thread Stack
from [AsyncGetCallTrace+0x3949c]
[0x00007f53cc1fd000 - 0x00007f53cc601000] committed 4112KB from [AsyncGetCallTrace+0x3949c]
[0x00007f53cc601000 - 0x00007f53cc71b000] reserved 1128KB for GC
from [JVM_handle_linux_signal+0x172529]
[0x00007f53cc601000 - 0x00007f53cc71b000] committed 1128KB from [dlerror+0x3aad37]
[0x00007f53cc71b000 - 0x00007f53cc81b000] reserved 1024KB for Code
from [JVM_handle_linux_signal+0x172289]
[0x00007f53cc71b000 - 0x00007f53cc75d000] committed 264KB from [JVM_handle_linux_signal+0x1746f4]
[0x00007f53cf497000 - 0x00007f53cf4a2000] reserved 44KB for GC
from [JVM_handle_linux_signal+0x172529]
[0x00007f53cf497000 - 0x00007f53cf54d000] committed 728KB from [JVM_handle_linux_signal+0x650ab]
[0x00007f53cf4a2000 - 0x00007f53cf54d000] reserved 684KB for GC
from [JVM_handle_linux_signal+0x172289]
[0x00007f53cf54d000 - 0x00007f53cf64e000] reserved 1028KB for Thread Stack
from [JVM_handle_linux_signal+0x12c997]
[0x00007f53cf54d000 - 0x00007f53cf64e000] committed 1028KB from [JVM_handle_linux_signal+0x12c997]
[0x00007f53cf656000 - 0x00007f53cf66f000] reserved 100KB for GC
from [JVM_handle_linux_signal+0x172289]
[0x00007f53cf656000 - 0x00007f53cf66f000] committed 100KB from [JVM_handle_linux_signal+0x650ab]
[0x00007f53cf66f000 - 0x00007f53cf677000] reserved 32KB for Internal
from [JVM_handle_linux_signal+0x3c924]
Details:
[0x00007f53ce330855] JVM_handle_linux_signal+0xee085
(malloc=6627KB #77628)
[0x00007f53ce291061] JVM_handle_linux_signal+0x4e891
(malloc=5120KB #5)
[0x00007f53ce293021] JVM_handle_linux_signal+0x50851
(malloc=5120KB #5)
[0x00007f53ce2a19b5] JVM_handle_linux_signal+0x5f1e5
(malloc=5120KB #5)
[0x00007f53ce1c8c64] JVM_FindSignal+0x1188f4
(malloc=4040KB #1)
[0x00007f53cde99851] dlerror+0x409851
(malloc=3903KB #5678)
[0x00007f53cdd2dcb3] dlerror+0x29dcb3
(malloc=2643KB #148)
[0x00007f53cdff5b86] AsyncGetCallTrace+0x6dc46
(malloc=2512KB #314)
[0x00007f53ce1c0b17] JVM_FindSignal+0x1107a7
(malloc=1274KB #106)
[0x00007f53ce291149] JVM_handle_linux_signal+0x4e979
(malloc=640KB #5)
[0x00007f53ce233375] JVM_FindSignal+0x183005
(malloc=524KB #419)
[0x00007f53ce38c670] JVM_handle_linux_signal+0x149ea0
(malloc=469KB #1)
[0x00007f53cde87c53] dlerror+0x3f7c53
(malloc=408KB #16085)
[0x00007f53cdd2d142] dlerror+0x29d142
(malloc=360KB #1)
[0x00007f53cdff5186] AsyncGetCallTrace+0x6d246
(malloc=310KB #25)
[0x00007f53ce38c581] JVM_handle_linux_signal+0x149db1
(malloc=156KB #1)
[0x00007f53cdd38523] dlerror+0x2a8523
(malloc=127KB #681)
[0x00007f53ce1c5acb] JVM_FindSignal+0x11575b
(malloc=96KB #2)
[0x00007f53ce1c807e] JVM_FindSignal+0x117d0e
(malloc=96KB #1)
[0x00007f53ce38e0e4] JVM_handle_linux_signal+0x14b914
(malloc=80KB #5)
[0x00007f53ce368abd] JVM_handle_linux_signal+0x1262ed
(malloc=71KB #25)
[0x00007f53ce1b4c27] JVM_FindSignal+0x1048b7
(malloc=64KB #16)
[0x00007f53ce1b4c97] JVM_FindSignal+0x104927
(malloc=64KB #16)
[0x00007f53ce25c867] JVM_handle_linux_signal+0x1a097
(malloc=55KB #116)
[0x00007f53ce1c0584] JVM_FindSignal+0x110214
(malloc=51KB #1)
[0x00007f53ce1c5a15] JVM_FindSignal+0x1156a5
(malloc=48KB #1)
[0x00007f53cdea0fc3] dlerror+0x410fc3
(malloc=37KB #464)
[0x00007f53cdf169bd] dlerror+0x4869bd
(malloc=36KB #13)
[0x00007f53ce3b2aa7] JVM_handle_linux_signal+0x1702d7
(malloc=24KB #13)
[0x00007f53cdff6496] AsyncGetCallTrace+0x6e556
(malloc=20KB #4)
[0x00007f53cdeb2ff3] dlerror+0x422ff3
(malloc=17KB #180)
[0x00007f53ce27ba1b] JVM_handle_linux_signal+0x3924b
(malloc=15KB #255)
[0x00007f53ce368b9d] JVM_handle_linux_signal+0x1263cd
(malloc=10KB #1)
[0x00007f53ce367fdb] JVM_handle_linux_signal+0x12580b
(malloc=8KB #47)
[0x00007f53cdff2df5] AsyncGetCallTrace+0x6aeb5
(malloc=8KB #11)
[0x00007f53cdf5d7d4] dlerror+0x4cd7d4
(malloc=8KB #1)
[0x00007f53ce289bc4] JVM_handle_linux_signal+0x473f4
(malloc=8KB #1)
[0x00007f53ce2059d6] JVM_FindSignal+0x155666
(malloc=7KB #62)
[0x00007f53ce27bb04] JVM_handle_linux_signal+0x39334
(malloc=7KB #251)
[0x00007f53ce242453] fork1+0x52b3
(malloc=6KB #28)
[0x00007f53ce024918] AsyncGetCallTrace+0x9c9d8
(malloc=5KB #18)
[0x00007f53cdd2d333] dlerror+0x29d333
(malloc=2KB #57)
[0x00007f53ce36a598] JVM_handle_linux_signal+0x127dc8
(malloc=2KB #1)
[0x00007f53ce2d6e24] JVM_handle_linux_signal+0x94654
(malloc=2KB #1)
[0x00007f53ce290d96] JVM_handle_linux_signal+0x4e5c6
(malloc=2KB #5)
[0x00007f53ce2a1536] JVM_handle_linux_signal+0x5ed66
(malloc=2KB #5)
[0x00007f53ce25a49b] JVM_handle_linux_signal+0x17ccb
(malloc=2KB #7)
[0x00007f53cde881eb] dlerror+0x3f81eb
(malloc=1KB #15)
[0x00007f53ce171720] JVM_FindSignal+0xc13b0
(malloc=1KB #74)
[0x00007f53cdf5ef54] dlerror+0x4cef54
(malloc=1KB #1)
[0x00007f53cde8a8aa] dlerror+0x3fa8aa
(malloc=1KB #59)
[0x00007f53ce3b658d] JVM_handle_linux_signal+0x173dbd
(mmap: reserved=575488KB, committed=574976KB)
[0x00007f53ce3b6975] JVM_handle_linux_signal+0x1741a5
(mmap: reserved=65536KB, committed=16832KB)
[0x00007f53ce3b4cf9] JVM_handle_linux_signal+0x172529
(mmap: reserved=20280KB, committed=20280KB)
[0x00007f53ce371abc] JVM_handle_linux_signal+0x12f2ec
(mmap: reserved=19532KB, committed=19532KB)
[0x00007f53cdfc13dc] AsyncGetCallTrace+0x3949c
(mmap: reserved=4112KB, committed=4112KB)
[0x00007f53ce3b4a59] JVM_handle_linux_signal+0x172289
(mmap: reserved=1808KB, committed=1048KB)
[0x00007f53ce1c928b] JVM_FindSignal+0x118f1b
(mmap: reserved=1028KB, committed=1028KB)
[0x00007f53ce36a3b9] JVM_handle_linux_signal+0x127be9
(mmap: reserved=1028KB, committed=1028KB)
[0x00007f53ce36f167] JVM_handle_linux_signal+0x12c997
(mmap: reserved=1028KB, committed=1028KB)
[0x00007f53ce3bf0dd] JVM_handle_linux_signal+0x17c90d
(mmap: reserved=1028KB, committed=1028KB)
[0x00007f53ce27f0f4] JVM_handle_linux_signal+0x3c924
(mmap: reserved=32KB, committed=0KB)
RES或%MEM值是物理内存的实际使用情况。
因为您的系统完全没有内存压力，所以不会尝试恢复物理内存。这是因为这样的努力是一个失败的提议。如果记忆没有很快被用于其他目的，那么释放它的努力就白费了。如果内存很快就被用于其他目的，那么释放内存的努力比浪费内存更糟糕，必须撤消它才能再次使用内存。当需要内存时，现代操作系统直接将内存从一种用途转换为另一种用途，而不必释放内存。只有在别无选择的情况下，记忆才会变得自由。
因此，基本上，在系统找到更好的用途之前，物理内存是暂时浪费的。如果你在消耗物理内存的机器上运行一些其他任务，你会看到RES和%MEM值随着物理内存转换到另一种用途而下降。