RFR: 8329223: Parallel: Parallel GC resizes heap even if -Xms = -Xmx [v7]

Thu Apr 25 13:42:32 UTC 2024

On Thu, 25 Apr 2024 10:00:16 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Debugging with following command line:
>> `make CONF=macosx-aarch64-server-fastdebug run-test TEST=gtest TEST_VM_OPTS="-Xlog:gc+heap=trace"`
>> 
>> With `initial_old_size = MinOldSize` fails this test:
>> 
>> ``` 
>>   // If OldSize is set on the command line, it should be used
>>   // for both min and initial old size if less than min heap.
>>   TestGenCollectorPolicy::SetOldSizeCmd setter(20 * M);
>> 
>>   TestGenCollectorPolicy::CheckOldMin checker_min(20 * M);
>>   TestGenCollectorPolicy::TestWrapper::test(&setter, &checker_min);
>> 
>> 
>> Debug output:
>> 
>> [0.001s][trace][gc,heap]   Maximum heap size 8589934592
>> [0.001s][trace][gc,heap]   Initial heap size 536870912
>> [0.001s][trace][gc,heap]   Minimum heap size 6815736
>> [0.008s][debug][gc,heap] Minimum heap 8388608  Initial heap 536870912  Maximum heap 8589934592
>> [0.036s][debug][gc,heap] Minimum heap 41943040  Initial heap 109051904  Maximum heap 8589934592
>> [0.036s][trace][gc,heap] 1: Minimum young 196608  Initial young 36306944  Maximum young 83886080
>> [0.036s][warning][gc,ergo] Inconsistency between initial old size and minimum old size
>> [0.036s][warning][gc,ergo] Inconsistency between generation sizes and heap size, resizing the generations to fit the heap.
>> [0.036s][trace  ][gc,heap] 2: Minimum young 196608  Initial young 67305472  Maximum young 83886080
>> [0.036s][trace  ][gc,heap] Minimum old 41746432  Initial old 41746432  Maximum old 8506048512
>> /Users/zhengyu.gu/ws/jdk/test/hotspot/gtest/gc/shared/test_collectorPolicy.cpp:261: Failure
>> 
>> 
>> 
>> With `MinOldSize = initial_old_size`
>> 
>> Debug output:
>> 
>> 
>> [0.001s][trace][gc,heap]   Maximum heap size 8589934592
>> [0.001s][trace][gc,heap]   Initial heap size 536870912
>> [0.001s][trace][gc,heap]   Minimum heap size 6815736
>> [0.007s][debug][gc,heap] Minimum heap 8388608  Initial heap 536870912  Maximum heap 8589934592
>> [0.034s][debug][gc,heap] Minimum heap 41943040  Initial heap 109051904  Maximum heap 8589934592
>> [0.034s][trace][gc,heap] 1: Minimum young 196608  Initial young 36306944  Maximum young 83886080
>> [0.034s][warning][gc,ergo] Inconsistency between initial old size and minimum old size
>> [0.034s][warning][gc,ergo] Inconsistency between generation sizes and heap size, resizing the generations to fit the heap.
>> [0.034s][trace  ][gc,heap] 2: Minimum young 196608  Initial young 83886080  Maximum young 83886080
>> [0.034s][trace  ][gc,heap] Minimum old 20971520  Initial old 25165824  Maximum old 8506048512
>> 
>> 
>> 
>> I will reverse b...
>
> I can see these lines are diff:
> 
> 
> [0.036s][trace  ][gc,heap] 2: Minimum young 196608  Initial young 67305472  Maximum young 83886080
> [0.036s][trace  ][gc,heap] Minimum old 41746432  Initial old 41746432  Maximum old 8506048512
> 
> 
> vs
> 
> 
> [0.034s][trace  ][gc,heap] 2: Minimum young 196608  Initial young 83886080  Maximum young 83886080
> [0.034s][trace  ][gc,heap] Minimum old 20971520  Initial old 25165824  Maximum old 8506048512
> 
> 
> Does that mean using values from the problematic case, sth like `-XX:MinHeapSize=41943040 -XX:InitialHeapSize=109051904 -XX:MaxHeapSize=8589934592 -XX:NewSize=67305472 -XX:MaxNewSize=83886080 -XX:OldSize=20m`, one would get failure on launching java from cmdline on macosx-aarch64? (These values from the log are printed after they are adjusted as I read the code, so the actual cmdline flag values might not be diff. If you can reproduce the failure consistently on your box, further instrumenting might be required.)
> 
> It's still unclear to how the failure is triggered. Therefore, I can't say whether `MinOldSize = initial_old_size` fixes the issue, or just hides it.

No, I believe it is the weirdness of the gtest. If I run from command line, both yield the same results:

`initial_old_size = MinOldSize`

MREM54BA45D6:hotspot zhengyu.gu$ $TEST_JDK/bin/java -XX:MinHeapSize=41943040 -XX:InitialHeapSize=109051904 -XX:MaxHeapSize=8589934592 -XX:NewSize=67305472 -XX:MaxNewSize=83886080 -XX:OldSize=20m -XX:+UseParallelGC -Xlog:gc+ergo,gc+heap=trace -version
[0.011s][debug][gc,heap] Minimum heap 41943040  Initial heap 109051904  Maximum heap 8589934592
[0.011s][trace][gc,heap] 1: Minimum young 41418752  Initial young 67108864  Maximum young 83886080
[0.011s][warning][gc,ergo] Inconsistency between generation sizes and heap size, resizing the generations to fit the heap.
[0.011s][trace  ][gc,heap] 2: Minimum young 41418752  Initial young 83886080  Maximum young 83886080
[0.011s][trace  ][gc,heap] Minimum old 524288  Initial old 25165824  Maximum old 8506048512
openjdk version "23-internal" 2024-09-17
OpenJDK Runtime Environment (fastdebug build 23-internal-adhoc.zhengyugu.jdk)
OpenJDK 64-Bit Server VM (fastdebug build 23-internal-adhoc.zhengyugu.jdk, mixed mode, sharing)
MREM54BA45D6:hotspot zhengyu.gu$ $TEST_JDK/bin/java  -XX:OldSize=20m -XX:+UseParallelGC -Xlog:gc+ergo,gc+heap=trace -version
[0.001s][trace][gc,heap]   Maximum heap size 8589934592
[0.001s][trace][gc,heap]   Initial heap size 536870912
[0.001s][trace][gc,heap]   Minimum heap size 22334664
[0.010s][debug][gc,heap] Minimum heap 25165824  Initial heap 536870912  Maximum heap 8589934592
[0.010s][trace][gc,heap] 1: Minimum young 1572864  Initial young 515899392  Maximum young 2863136768
[0.010s][trace][gc,heap] Minimum old 20971520  Initial old 20971520  Maximum old 5726797824
openjdk version "23-internal" 2024-09-17
OpenJDK Runtime Environment (fastdebug build 23-internal-adhoc.zhengyugu.jdk)
OpenJDK 64-Bit Server VM (fastdebug build 23-internal-adhoc.zhengyugu.jdk, mixed mode, sharing)

`MinOldSize = initial_old_size;`

MREM54BA45D6:hotspot zhengyu.gu$ $TEST_JDK/bin/java -XX:MinHeapSize=41943040 -XX:InitialHeapSize=109051904 -XX:MaxHeapSize=8589934592 -XX:NewSize=67305472 -XX:MaxNewSize=83886080 -XX:OldSize=20m -XX:+UseParallelGC -Xlog:gc+ergo,gc+heap=trace -version
[0.014s][debug][gc,heap] Minimum heap 41943040  Initial heap 109051904  Maximum heap 8589934592
[0.014s][trace][gc,heap] 1: Minimum young 41418752  Initial young 67108864  Maximum young 83886080
[0.014s][warning][gc,ergo] Inconsistency between generation sizes and heap size, resizing the generations to fit the heap.
[0.014s][trace  ][gc,heap] 2: Minimum young 41418752  Initial young 83886080  Maximum young 83886080
[0.014s][trace  ][gc,heap] Minimum old 524288  Initial old 25165824  Maximum old 8506048512
openjdk version "23-internal" 2024-09-17
OpenJDK Runtime Environment (fastdebug build 23-internal-adhoc.zhengyugu.jdk)
OpenJDK 64-Bit Server VM (fastdebug build 23-internal-adhoc.zhengyugu.jdk, mixed mode, sharing)
MREM54BA45D6:hotspot zhengyu.gu$ $TEST_JDK/bin/java  -XX:OldSize=20m -XX:+UseParallelGC -Xlog:gc+ergo,gc+heap=trace -version
[0.002s][trace][gc,heap]   Maximum heap size 8589934592
[0.002s][trace][gc,heap]   Initial heap size 536870912
[0.002s][trace][gc,heap]   Minimum heap size 22334664
[0.015s][debug][gc,heap] Minimum heap 25165824  Initial heap 536870912  Maximum heap 8589934592
[0.015s][trace][gc,heap] 1: Minimum young 1572864  Initial young 515899392  Maximum young 2863136768
[0.015s][trace][gc,heap] Minimum old 20971520  Initial old 20971520  Maximum old 5726797824
openjdk version "23-internal" 2024-09-17
OpenJDK Runtime Environment (fastdebug build 23-internal-adhoc.zhengyugu.jdk)
OpenJDK 64-Bit Server VM (fastdebug build 23-internal-adhoc.zhengyugu.jdk, mixed mode, sharing)

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PR Review Comment: https://git.openjdk.org/jdk/pull/18539#discussion_r1579492865