RFR: 8238665: Add JFR event for direct memory statistics

[Erik Gahlin]

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> 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>
> 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>; Erik Gahlin <erik.gahlin at oracle.com>; hotspot-jfr-dev <hotspot-jfr-dev at openjdk.java.net>; core-libs-dev <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.