Request for review: 6976350 G1: deal with fragmentation while copying objects during GC

[Jon Masamitsu]

http://cr.openjdk.java.net/~tamao/6976350/webrev.00/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp.frames.html

line 4386

Please add the brackets for the outer for loop.  I'm not used to seeing it
without the brackets even though they are not strictly needed.

http://cr.openjdk.java.net/~tamao/6976350/webrev.00/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp.frames.html

line 1821 same comment about brackets for for-statement.

line 1869

You always retire alloc_buf1.  Did you consider retiring the buffer that 
has the
less words_remaining?

line 1762

Can you make _alloc_buffers two dimensional?  Then you wouldn't need the
buf_idx() method.

GCAllocPriority is an enum but you use them as integers in the for loops.
Can you make the for loop index variable an enum GCAllocPriority?

Jon





On 1/28/2013 12:21 PM, Tao Mao wrote:
> 6976350 G1: deal with fragmentation while copying objects during GC
> https://jbs.oracle.com/bugs/browse/JDK-6976350
>
> webrev:
> http://cr.openjdk.java.net/~tamao/6976350/webrev.00/
>
> changeset:
> Basically, we want to reuse more of par-allocation buffers instead of 
> retiring it immediately when it encounters an object larger than its 
> remaining part.
>
> (1) instead of previously using one allocation buffer per GC purpose, 
> we use N(=2) buffers per GC purpose and modify the corresponding code. 
> The changeset would easily scale up to whatever N (though Tony 
> Printezis suggests 2, or 3 may be good enough)
>
> *(2) Two places of cleanup: allocate_during_gc_slow() is removed due 
> to its never being called.
>                                               access modifier (public) 
> before trim_queue() is redundant.
>
>