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

[Erik Helin]

Hi Mikael and Stefan,

thanks for having a look and special thanks to Mikael for finding the bug!

Please see new webrev at:
http://cr.openjdk.java.net/~ehelin/8036703/webrev.04/

Please see the incremental webrev at:
http://cr.openjdk.java.net/~ehelin/8036703/webrev.03-04/

Based on some internal feedback, I also corrected a few nits (see the 
incremental webrev for details).

Thanks,
Erik

On 2014-03-13 10:40, Stefan Karlsson wrote:
>
> On 2014-03-13 09:57, Mikael Gerdin wrote:
>> Hi Erik,
>>
>> On Wednesday 12 March 2014 17.04.26 Erik Helin wrote:
>>> 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/
>> I think this version is much better!
>> Just a small issue:
>>
>> collectedHeap.cpp
>>    99
>>   100   const MetaspaceChunkFreeListSummary& ms_chunk_free_list_summary =
>>   101     MetaspaceAux::chunk_free_list_summary(Metaspace::ClassType);
>>   102   const MetaspaceChunkFreeListSummary&
>> class_chunk_free_list_summary =
>>   103     MetaspaceAux::chunk_free_list_summary(Metaspace::NonClassType);
>>   104
>> It looks like you pass the wrong MetadataType to
>> chunk_free_list_summary here,
>> ClassType and NonClassType should be swapped.
>
> Except for this bug, this looks good.
>
> thanks,
> StefanK
>
>>
>> /Mikael
>>
>>> 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
>