Request for review (m) - 8008508: CMS does not correctly reduce heap size after a Full GC

[Jon Masamitsu]

On 2/25/2013 3:48 PM, John Cuthbertson wrote:
> Hi Jon,
>
> This looks good to me except you have left some instrumentation in 
> generation.cpp:
>
>>   597     // We have two shrinking computations, take the largest
>>   598     shrink_bytes = MAX2(shrink_bytes, expansion_for_promotion);
>>   599     assert(shrink_bytes <= max_shrink_bytes, "invalid shrink 
>> size");
>>   600 if (true || PrintGC && Verbose) {

Oops.  Fixed.

>>   601       gclog_or_tty->print_cr("  "
>>   602                              "  aggressive shrinking:"
>>   603                              "  _capacity_at_prologue: %.1fK"
>>   604                              "  capacity_after_gc: %.1fK"
>>   605                              "  expansion_for_promotion: %.1fK"
>>   606                              "  shrink_bytes: %.1fK",
>>   607                              capacity_after_gc / (double) K,
>>   608                              _capacity_at_prologue / (double) K,
>>   609                              expansion_for_promotion / (double) K,
>>   610                              shrink_bytes / (double) K);
>>   611     }
>
> and I don't think you need:
>
>> 1083
>> 1084   TenuredGeneration* as_TenuredGeneration() { return 
>> (TenuredGeneration*) this; }
>> 1085
> in ConcurrentMarkSweepGeneration.hpp anymore.

Right again.  Fixed.

Jon
>
> JohnC
>
> On 2/19/2013 9:29 PM, Jon Masamitsu wrote:
>> 8008508: CMS does not correctly reduce heap size after a Full GC
>>
>> http://cr.openjdk.java.net/~jmasa/8008508/webrev.00/
>>
>> The CMS generation has a CompactibleFreeListSpace that describes
>> its part of the heap space.  The free space of a 
>> CompactibleFreeListSpace
>> is maintained in freelists and it is cannot shrink in the simple
>> the ContiguousSpaces shrink.  The exception is after a full GC when
>> all the free space in the CMS geneartion is in a single chunk at the
>> end of the CompactibleFreeListSpace. This change treats the free space
>> in the CMS generation like a ContiguousSpace and shrinks it using the
>> same policy as many of the other generations.
>>
>> Move the method compute_new_size() from the TenuredGeneration into
>> the CardGeneration when it can be shared with the 
>> ConcMarkSweepGeneration.
>> Some associated variables are also moved.
>>
>> Added a compute_new_space_free_list() and associated methods for
>> managing the size of the CompactibleFreeListSpace in the CMS generation.
>> The method shrink_free_list_by() still does not shrink the CMS 
>> generation.
>>
>> Thanks.
>