[jmm-dev] official docs about metaspace

[刘波]

hi, 
where's the office documents about metaspace ?


I want to know what's metaspace? what's it stores? how it's working? where can I find docs about metaspace?


openjdk website search "metaspace" got lots of messages, does anyone know the official docs about metaspace, or any docs about it?
 
I search all the jdk 8 documentation: none of there files talk about metaspace
 
grep -rnw ./* -e "Metaspace" --col                                                                18:43:54 
 
./technotes/tools/unix/jstat.html:210:<p><code dir="ltr">MC</code>: Metaspace capacity (kB).</p>
 
./technotes/tools/unix/jstat.html:235:<p><code dir="ltr">MC</code>: Metaspace capacity (kB).</p>
 
./technotes/tools/unix/jstat.html:281:<p><code dir="ltr">MC</code>: Metaspace capacity (kB).</p>
 
./technotes/tools/unix/jstat.html:282:<p><code dir="ltr">MU</code>: Metaspace utilization (kB).</p>
 
./technotes/tools/unix/jstat.html:306:<p>Metaspace size statistics.</p>
 
./technotes/tools/unix/jstat.html:309:<p><code dir="ltr">MC</code>: Metaspace capacity (kB).</p>
 
./technotes/tools/unix/jstat.html:324:<p><code dir="ltr">M</code>: Metaspace utilization as a percentage of the space's current capacity.</p>
 
./technotes/tools/windows/jstat.html:210:<p><code dir="ltr">MC</code>: Metaspace capacity (kB).</p>
 
./technotes/tools/windows/jstat.html:235:<p><code dir="ltr">MC</code>: Metaspace capacity (kB).</p>
 
./technotes/tools/windows/jstat.html:281:<p><code dir="ltr">MC</code>: Metaspace capacity (kB).</p>
 
./technotes/tools/windows/jstat.html:282:<p><code dir="ltr">MU</code>: Metaspace utilization (kB).</p>
 
./technotes/tools/windows/jstat.html:306:<p>Metaspace size statistics.</p>
 
./technotes/tools/windows/jstat.html:309:<p><code dir="ltr">MC</code>: Metaspace capacity (kB).</p>
 
./technotes/tools/windows/jstat.html:324:<p><code dir="ltr">M</code>: Metaspace utilization as a percentage of the space's current capacity.</p>
 
./technotes/guides/troubleshoot/memleaks002.html:98:<dt><span><a id="sthref42" name="sthref42"/>Exception in thread <span>thread_name</span>: java.lang.OutOfMemoryError: Metaspace</span> </dt>
 
./technotes/guides/troubleshoot/memleaks002.html:132:<p><b>Note:</b> There is more than one kind of class metadata - <code dir="ltr">klass</code> metadata and other metadata. Only <code dir="ltr">klass</code> metadata is stored in the space bounded by <code dir="ltr">CompressedClassSpaceSize</code>. The other metadata is stored in <code dir="ltr">Metaspace</code>.</p>
 
./technotes/guides/vm/gctuning/considerations.html:97:  Metaspace       used 2425K, capacity 4498K, committed 4864K, reserved 1056768K
 
./technotes/guides/vm/gctuning/considerations.html:100:<p>In the line beginning with <code dir="ltr">Metaspace</code>, the <code dir="ltr">used</code> value is the amount of space used for loaded classes. The <code dir="ltr">capacity</code> value is the space available for metadata in currently allocated chunks. The <code dir="ltr">committed</code> value is the amount of space available for chunks. The <code dir="ltr">reserved</code> value is the amount of space reserved (but not necessarily committed) for metadata. The line beginning with <code dir="ltr">class space</code> line contains the corresponding values for the metadata for compressed class pointers.</p>