[11] RFR(S): 8205499: C1 temporary code buffers are not removed with -XX:+UseDynamicNumberOfCompilerThreads

[Tobias Hartmann]

Thanks, Vladimir.

Best regards,
Tobias

On 28.06.2018 19:22, Vladimir Kozlov wrote:
> Looks good.
> 
> Thanks,
> Vladimir
> 
> On 6/28/18 3:39 AM, Tobias Hartmann wrote:
>> Hi,
>>
>> please review the following patch:
>> https://bugs.openjdk.java.net/browse/JDK-8205499
>> http://cr.openjdk.java.net/~thartmann/8205499/webrev.00/
>>
>> The problem is that with -XX:+UseDynamicNumberOfCompilerThreads, compiler threads are dynamically
>> created and removed but the C1 temporary code buffers are not deallocated. As a result, the code
>> cache fills up with long running applications, disabling compilation.
>>
>> I was able to reproduce this by slightly modifying the code such that compiler threads are
>> aggressively added and removed. The code cache quickly fills up and we get the expected warning [1].
>> I was not able to create a stable regression test because that would require to alternate between
>> generating compilation tasks and waiting for compiler threads to become idle and get removed (i.e.,
>> the test would be long running).
>>
>> The fix is to deallocate the code buffers in the thread destructor. I've verified that this solves
>> the issue.
>>
>> Thanks,
>> Tobias
>>
>> [1] Java HotSpot(TM) 64-Bit Server VM warning: CodeCache is full. Compiler has been disabled.
>> Java HotSpot(TM) 64-Bit Server VM warning: Try increasing the code cache size using
>> -XX:ReservedCodeCacheSize=
>> CodeCache: size=51200Kb used=50978Kb max_used=50990Kb free=221Kb
>>   bounds [0x00007fd068e00000, 0x00007fd06c000000, 0x00007fd06c000000]
>>   total_blobs=1284 nmethods=237 adapters=787
>>   compilation: disabled (not enough contiguous free space left)
>>                stopped_count=1, restarted_count=0
>>   full_count=0
>> Java HotSpot(TM) 64-Bit Server VM warning: Initialization of C1 CompilerThread3 thread failed (no
>> space to run compilers)
>> Java HotSpot(TM) 64-Bit Server VM warning: Initialization of C1 CompilerThread5 thread failed (no
>> space to run compilers)
>> Java HotSpot(TM) 64-Bit Server VM warning: Initialization of C1 CompilerThread4 thread failed (no
>> space to run compilers)
>>