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

[Stefan Karlsson]

On 2014-03-13 14:00, Erik Helin wrote:
> 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/

Looks good.

StefanK

>
> 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
>>