Calculating JIT compilation time

[mehra.a...@gmail.com]

Hi all,

Is there a way in OpenJDK+Hotspot to determine how much time is spent by JIT threads in compiling the methods?

Does JITWatch provide this information? I know it provides a histogram "JIT Compilation Times" but I actually need the cumulative time.

Any help is appreciated!

Thanks,

Ashutosh Mehra

[Chris Newland]

Hi Ashutosh,

HotSpot will tell you this directly if you add the flag

-XX:+CITime

Example output from running java -XX:+CITime without a class or jar name:

Accumulated compiler times (for compiled methods only)

------------------------------------------------

  Total compilation time   :  0.013 s

    Standard compilation   :  0.013 s, Average : 0.000

    On stack replacement   :  0.000 s, Average : -nan

    Detailed C1 Timings

       Setup time:         0.000 s ( 0.0%)

       Build IR:           0.003 s (39.0%)

         Optimize:            0.000 s ( 2.6%)

         RCE:                 0.000 s ( 0.8%)

       Emit LIR:           0.004 s (40.8%)

         LIR Gen:           0.001 s ( 8.3%)

         Linear Scan:       0.003 s (32.1%)

       LIR Schedule:       0.000 s ( 0.0%)

       Code Emission:      0.001 s (12.9%)

       Code Installation:  0.001 s ( 7.2%)

       Instruction Nodes:   2454 nodes

  Total compiled methods   :     51 methods

    Standard compilation   :     51 methods

    On stack replacement   :      0 methods

  Total compiled bytecodes :   3298 bytes

    Standard compilation   :   3298 bytes

    On stack replacement   :      0 bytes

  Average compilation speed: 260427 bytes/s

  nmethod code size        :  48096 bytes

  nmethod total size       :  77480 bytes

JITWatch does provide timing information in various places but doesn't give a nice detailed summary like this!

Cheers,

Chris

[ashutosh mehra]

That's exactly I wanted. Thanks Chris!

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