RFR: 8373114: Redundant MethodCounters in the preimage generated by training run [v3]

[Ashutosh Mehra]

On Tue, 9 Dec 2025 02:39:41 GMT, Ashutosh Mehra <asmehra at openjdk.org> wrote:

>> Details are mentioned in the bug report and this mail thread https://mail.openjdk.org/pipermail/leyden-dev/2025-December/002843.html
>> After this patch the number of MethodCounters in the preimage are much less than before this patch. Also the number of MethodCounters in the preimage is the same as in the final AOTCache (these numbers are obtained using -Xlog:aot=trace).
>> 
>> Before this patch for the training run:
>> 
>> [18.610s][debug  ][aot         ]                         ro_cnt   ro_bytes     % |   rw_cnt   rw_bytes     % |  all_cnt  all_bytes     %
>> [18.610s][debug  ][aot         ] MethodCounters      :        0          0   0.0 |    22471    1438144   6.2 |    22471    1438144   2.6
>> 
>> Before this patch for the assembly phase:
>> 
>> [6.680s][debug][aot         ]                         ro_cnt   ro_bytes     % |   rw_cnt   rw_bytes     % |  all_cnt  all_bytes     %
>> [6.680s][debug][aot         ] MethodCounters      :        0          0   0.0 |     8588     549632   2.5 |     8588     549632   1.0
>> 
>> 
>> After this patch for the training run:
>> 
>> [49.371s][debug  ][aot         ]                         ro_cnt   ro_bytes     % |   rw_cnt   rw_bytes     % |  all_cnt  all_bytes     %
>> [49.371s][debug  ][aot         ] MethodTrainingData  :        0          0   0.0 |     4658     521696   2.1 |     4658     521696   0.9
>> 
>> 
>> After this patch for the assembly phase:
>> 
>> [12.580s][debug][aot         ]                         ro_cnt   ro_bytes     % |   rw_cnt   rw_bytes     % |  all_cnt  all_bytes     %
>> [12.580s][debug][aot         ] MethodTrainingData  :        0          0   0.0 |     4658     521696   2.1 |     4658     521696   0.9
>
> Ashutosh Mehra has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove blank line
>   
>   Signed-off-by: Ashutosh Mehra <asmehra at redhat.com>

Before the patch with mainline:
In pre-image:

[19.021s][debug  ][aot         ]                         ro_cnt   ro_bytes     % |   rw_cnt   rw_bytes     % |  all_cnt  all_bytes     %
[19.021s][debug  ][aot         ] MethodCounters      :        0          0   0.0 |    22485    1439040   6.2 |    22485    1439040   2.6
[19.021s][debug  ][aot         ] MethodTrainingData  :        0          0   0.0 |     4998     519792   2.2 |     4998     519792   0.9

In final AOTCache:


[6.655s][debug][aot         ]                         ro_cnt   ro_bytes     % |   rw_cnt   rw_bytes     % |  all_cnt  all_bytes     %  
[6.655s][debug][aot         ] MethodCounters      :        0          0   0.0 |     8535     546240   2.5 |     8535     546240   1.0
[6.655s][debug][aot         ] MethodTrainingData  :        0          0   0.0 |     4998     519792   2.3 |     4998     519792   1.0


After the new fix, I see following stats:

In pre-image:

[12.397s][debug  ][aot         ]                         ro_cnt   ro_bytes     % |   rw_cnt   rw_bytes     % |  all_cnt  all_bytes     %
[12.397s][debug  ][aot         ] MethodCounters      :        0          0   0.0 |     5440     348160   1.6 |     5440     348160   0.6
[12.397s][debug  ][aot         ] MethodTrainingData  :        0          0   0.0 |     4985     518440   2.3 |     4985     518440   1.0


In final AOTCache:

[7.452s][debug][aot         ]                         ro_cnt   ro_bytes     % |   rw_cnt   rw_bytes     % |  all_cnt  all_bytes     %
[7.452s][debug][aot         ] MethodCounters      :        0          0   0.0 |     4942     316288   1.4 |     4942     316288   0.6
[7.452s][debug][aot         ] MethodTrainingData  :        0          0   0.0 |     4985     518440   2.3 |     4985     518440   1.0


So the size of MethodCounters is 2.6% (before fix) vs 0.6% (after fix) in the preimage, and 1% (before fix) vs 0.6% (after fix) in the AOTCache.

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PR Comment: https://git.openjdk.org/jdk/pull/28670#issuecomment-3632961425