RFR: 8238665: Add JFR event for direct memory statistics

[Erik Gahlin]

Yes, I think it is fine to export from java.base to jdk.jfr for this 
feature.

If you would add support for other buffer pools, it should not be over 
MXBeans, but using classes/interfaces that is available in java.base.

Erik

On 2020-03-05 16:19, Denghui Dong wrote:
> Hi Alan and Erik,
>
> Sorry, I'm not sure if I fully understand what you mean.
> For this feature, I still think exporting jdk.internal.access to jdk.jfr is a good solutionsince there are
> some other packages has already exported to jdk.jfr in this module.
>
> Thanks,
> Denghui Dong
>
>     ------------------------------------------------------------------
>     From:Erik Gahlin <erik.gahlin at oracle.com>
>     Send Time:2020年3月5日(星期四) 19:55
>     To:董登辉(卓昂) <denghui.ddh at alibaba-inc.com>
>     Cc:hotspot-jfr-dev <hotspot-jfr-dev at openjdk.java.net>;
>     core-libs-dev <core-libs-dev at openjdk.java.net>; Alan Bateman
>     <Alan.Bateman at oracle.com>
>     Subject:Re: RFR: 8238665: Add JFR event for direct memory statistics
>
>     We should avoid adding a dependency on java.management. The
>     jdk.jfr module today only depends java.base so JFR can be used in
>     constrained environments. All JMX related functionality is in
>     jdk.management.jfr.
>
>     Erik
>
>     On 5 Mar 2020, at 10:54, Denghui Dong <denghui.ddh at alibaba-inc.com
>     <mailto:denghui.ddh at alibaba-inc.com>> wrote:
>
>     Hi Alan,
>
>     If I use ManagementFactoryHelper to get memory pools, I still
>     need to modify src/java.management/share/classes/module-info.java
>     to export sun.management, right?
>
>     Thanks,
>     Denghui Dong
>     ------------------------------------------------------------------
>     From:Alan Bateman <Alan.Bateman at oracle.com
>     <mailto:Alan.Bateman at oracle.com>>
>     Send Time:2020年3月5日(星期四) 16:46
>     To:董登辉(卓昂) <denghui.ddh at alibaba-inc.com
>     <mailto:denghui.ddh at alibaba-inc.com>>; Erik Gahlin
>     <erik.gahlin at oracle.com <mailto:erik.gahlin at oracle.com>>;
>     hotspot-jfr-dev <hotspot-jfr-dev at openjdk.java.net
>     <mailto:hotspot-jfr-dev at openjdk.java.net>>; core-libs-dev
>     <core-libs-dev at openjdk.java.net
>     <mailto:core-libs-dev at openjdk.java.net>>
>     Subject:Re: RFR: 8238665: Add JFR event for direct memory statistics
>
>     On 05/03/2020 02:44, Denghui Dong wrote:
>     > Hi Erik,
>     > Updated.
>     > Webrev: http://cr.openjdk.java.net/~ddong/8238665/webrev.01/
>     >
>     ManagementFactoryHelper has a method to get the list of MXBeans for the
>
>     buffer pools. That could be easily changed to return an unmodifable
>     list. That would allow you to emit statistics for memory-mapped files
>     too (the current patch seems to be limited to emitting stats for direct
>
>     buffers).
>
>     -Alan.
>