CRR: 7032531: G1: enhance GC logging to include more accurate eden / survivor size transitions (S/XS)

[Tony Printezis]

Poonam,

Yes, the whole heap can grow at the end of a young GC in G1.

Tony

On 06/08/2011 05:14 AM, Poonam Bajaj wrote:
> Hi Tony,
>
> On 6/7/2011 11:40 PM, Tony Printezis wrote:
>> Hi all,
>>
>> Could I have a couple of reviews for this change?
>>
>> http://cr.openjdk.java.net/~tonyp/7032531/webrev.0/
>>
>> This enhances the G1 +PrintGCDetails output to include how much space 
>> there is in the eden and survivor regions before / after a GC. Here's 
>> an example of the output:
>>
>>    [Eden: 18M->0B Survivors: 1024K->2048K Heap: 27M(105M)->12M(125M)]
>>
>> It shows that the eden had 18MB before the GC and it's empty after it 
>> (as expected!), the survivors were 1MB before the GC and grew to 2MB 
>> after the GC, the used space in the heap fell from 27MB to 12MB, and 
>> finally the heap size grew from 105MB to 125MB.
>>
> The heap size ( grew from 105K to 125K) here means the total size of 
> all the regions in G1 heap (including young regions) ?
>
> Thanks,
> Poonam
>
>> Note that, currently, the eden / survivor sizes that are reported are 
>> not very accurate. They are currently calculated as region_num * 
>> region_size. It'd be better if they were calculated as the used byte 
>> total in the eden and survivor regions. But this would require a fair 
>> amount of extra changes to do (I'd rather avoid iterating over them 
>> to calculate that). We'll do that change when we revamp the region 
>> lists that keep track of the eden / survivor regions (which is 
>> currently work-in-progress).
>>
>> Tony
>>
>
> -- 
> Best regards, Poonam
>
> Sun, an Oracle company
> Sun, an Oracle Company
> Poonam Bajaj | Staff Engineer
> Phone: +66937451 <tel:+66937451> | Mobile: +9844511366 <tel:+9844511366>
> JVM Sustaining Engineering
> | Bangalore
> Green Oracle <http://www.oracle.com/commitment> Oracle is committed to 
> developing practices and products that help protect the environment
>
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