RFR: 8036703: Add trace event with statistics for the metaspace chunk free lists

[Erik Helin]

Based on feedback from Mikael and StefanK, I've reworked the patch to 
put the ChunkFreeListSummaries in the class MetaspaceSummary.

Please see the new version at:
http://cr.openjdk.java.net/~ehelin/8036703/webrev.03/

Thanks,
Erik

On 2014-03-06 11:56, Erik Helin wrote:
> A small bug had found its way into this patch:
>
> metaspace.cpp:
> +bool MetaspaceAux::has_chunk_free_list(Metaspace::MetadataType mdtype) {
> +  return Metaspace::get_chunk_manager(mdtype) == NULL;
> +}
>
> should of course be:
>
> +bool MetaspaceAux::has_chunk_free_list(Metaspace::MetadataType mdtype) {
> +  return Metaspace::get_chunk_manager(mdtype) != NULL;
> +}
>
> Please see new webrev at:
> http://cr.openjdk.java.net/~ehelin/8036703/webrev.01/
>
> Thanks,
> Erik
>
> On 2014-03-06 10:35, Erik Helin wrote:
>> Hi all,
>>
>> this patch adds a new trace event -
>> vm/gc/metaspace/chunk_free_list_summary for getting statistics for
>> metaspace's chunk free lists. The event contains the numbers of chunks
>> in the free list and the size of the chunks in the free lists. This
>> information is provided for all different kinds of chunks - special,
>> small, medium and humongous.
>>
>> This information will be useful when diagnosing fragmentation issues in
>> metaspace.
>>
>> Webrev:
>> http://cr.openjdk.java.net/~ehelin/8036703/webrev.00/
>>
>> Enhancement:
>> https://bugs.openjdk.java.net/browse/JDK-8036703
>>
>> Testing:
>> - JFR JTREG tests
>> - JPRT
>> - Manually verifying that the numbers look correct by looking at
>>    recordings from small test cases.
>>
>> Thanks,
>> Erik