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The diagnostic options -XX:+LogCompilation emits a structured XML log
of compilation related activity during a run of the virtual machine.
By default it ends up in the standard hotspot.log file, though this
can be changed using the -XX:LogFile= option. Note that both of these
are considered diagnostic options and have to be enabled using
-XX:+UnlockDiagnosticVMOptions. Note that support for this by the
client compiler is incomplete so it will not report any inlining decisions.
The log actually consists of two parts. The main log is output from
normal Java threads and contains events for methods being enqueued for
compilation, uncommon traps that invalidate a method and other events.
The other part of the log comes from the compiler threads themselves.
During the execution the compiler threads write their logs to
temporary files with names of the form hs_c#_<pid>.log where # is the
number of the thread using by the compiler thread. At VM shutdown the
separate logs are appended onto the main hotspot.log to form the final
complete log.
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