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

[Erik Helin]

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