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

[Stefan Karlsson]

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