Merge pull request #774 from notpeter/java-tools

Java debug tools. Jstack, jmap and jhat.

pages/common/jhat.md

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+# jhat
+
+> Java Heap Analysis Tool.
+
+- Analyze a heap dump (from jmap), view via http on port 7000:
+
+`jhat {{dump_file.bin}}`
+
+- Analyze a heap dump, specifying an alternate port for the http server:
+
+`jhat -p {{port}} {{dump_file.bin}}`

pages/common/jmap.md

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+# jmap
+
+> Java Memory Map Tool.
+
+- Print shared object mappings for a java process (output like pmap):
+
+`jmap {{java_pid}}`
+
+- Print heap summary information:
+
+`jmap -heap {{filename.jar}} {{java_pid}}`
+
+- Print histogram of heap usage by type:
+
+`jmap -histo {{java_pid}}`
+
+- Dump contents of the heap into a binary file for analysis with jhat:
+
+`jmap -dump:format=b,file={{filename}} {{java_pid}}`

pages/common/jstack.md

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+# jstack
+
+> Java Stack Trace Tool.
+
+- Print java stack traces for all threads in a java process:
+
+`jstack {{java_pid}}`
+
+- Print mixed mode (java/c++) stack traces for all threads in a java process:
+
+`jstack -m {{java_pid}}`
+
+- Print stack traces from java core dump:
+
+`jstack {{/usr/bin/java}} {{file.core}}`