[9] RFR(S): 8065334: CodeHeap expansion fails although there is uncommitted memory

[Tobias Hartmann]

Hi,

please review the following patch:

https://bugs.openjdk.java.net/browse/JDK-8065334
http://cr.openjdk.java.net/~thartmann/8065334/webrev.00/

If ReservedCodeCacheSize (or the size of a single code heap) is not a multiple of CodeCacheExpansionSize, the last code heap expansion fails, leaving unused uncommitted memory. For example, see [1]. Both the profiled and the non-profiled segments are full but there is still 32Kb of uncommitted space that is never used (CodeCacheExpansionSize is 64Kb).

CodeHeap::expand_by() should check for this condition and commit all the remaining space even if the requested expansion size is larger. Like this, we use all the available space [2].

Thanks,
Tobias


[1] Baseline:
CodeHeap 'non-nmethods': size=5696Kb used=2403Kb max_used=2433Kb free=3292Kb
 bounds [0x00007f4d83b27000, 0x00007f4d83d97000, 0x00007f4d840b7000]
CodeHeap 'profiled nmethods': size=120032Kb used=119999Kb max_used=119999Kb free=32Kb
 bounds [0x00007f4d840b7000, 0x00007f4d8b5e7000, 0x00007f4d8b5ef000]
CodeHeap 'non-profiled nmethods': size=120032Kb used=119999Kb max_used=119999Kb free=32Kb
 bounds [0x00007f4d8b5ef000, 0x00007f4d92b1f000, 0x00007f4d92b27000]
 total_blobs=248449 nmethods=52 adapters=570
 compilation: disabled (not enough contiguous free space left)

[2] Fixed:
CodeHeap 'non-nmethods': size=5696Kb used=2404Kb max_used=2436Kb free=3291Kb
 bounds [0x00007fe8cd000000, 0x00007fe8cd270000, 0x00007fe8cd590000]
CodeHeap 'profiled nmethods': size=120032Kb used=120031Kb max_used=120031Kb free=0Kb
 bounds [0x00007fe8cd590000, 0x00007fe8d4ac8000, 0x00007fe8d4ac8000]
CodeHeap 'non-profiled nmethods': size=120032Kb used=120032Kb max_used=120032Kb free=0Kb
 bounds [0x00007fe8d4ac8000, 0x00007fe8dc000000, 0x00007fe8dc000000]
 total_blobs=10665 nmethods=127 adapters=570
 compilation: disabled (not enough contiguous free space left)