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

[Stefan Karlsson]

On 2014-03-06 17:16, Erik Helin wrote:
> Hi Stefan,
>
> thanks for reviewing! Please see comments inline and the new webrev at:
> http://cr.openjdk.java.net/~ehelin/8036703/webrev.02/

The updates look good.

StefanK

>
> On 2014-03-06 11:02, Stefan Karlsson wrote:
>>
>> 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/
>>
>> http://cr.openjdk.java.net/~ehelin/8036703/webrev.00/src/share/vm/gc_interface/collectedHeap.cpp.udiff.html 
>>
>>
>>
>> This isn't used:
>>
>> +  MetaspaceChunkFreeListSummary chunk_free_list_summary;
>
> Fixed.
>
> On 2014-03-06 11:02, Stefan Karlsson wrote:
>> http://cr.openjdk.java.net/~ehelin/8036703/webrev.00/src/share/vm/memory/metaspace.cpp.udiff.html 
>>
>>
>>
>> +  void index_bounds_check(ChunkIndex index) const {
>>
>> Should be static. Or maybe a #define if you want to get the line where
>> the assert happens.
>
> Agree, I turned it into a macro to get the correct line numbers in an 
> eventual hs_err file (good if the build is lacking debug symbols).
>
> On 2014-03-06 11:02, Stefan Karlsson wrote:
>> err_msg("Bad index: " INT32_FORMAT, (int) index));
>>
>> Should be %d instead of INT32_FORMAT.
>
> Fixed.
>
> On 2014-03-06 11:02, Stefan Karlsson wrote:
>> 2682   return
>> MetaspaceChunkFreeListSummary(cm->num_free_chunks(SpecializedIndex),
>> 2683
>> cm->num_free_chunks(SmallIndex),
>> 2684
>> cm->num_free_chunks(MediumIndex),
>> 2685
>> cm->num_free_chunks(HumongousIndex),
>> 2686
>> cm->size_free_chunks_in_bytes(SpecializedIndex),
>> 2687
>> cm->size_free_chunks_in_bytes(SmallIndex),
>> 2688
>> cm->size_free_chunks_in_bytes(MediumIndex),
>> 2689
>> cm->size_free_chunks_in_bytes(HumongousIndex));
>>
>> I think it's better to keep the setup of MetaspaceChunkFreeListSummary
>> in ChunkManager.
>
> Agree, I've added the method ChunkManager::chunk_free_list_summary.
>
> On 2014-03-06 11:02, Stefan Karlsson wrote:
>> Otherwise, this looks good.
>
> Thanks!
> Erik
>
>> thanks,
>> StefanK
>>
>>>
>>> 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
>>