Those memory footprint improvements in JDK 18

[Stefan Reich]

Ah, so the memory sections that are now smaller are basically the GC's
internal data structures, rather than the general heap?

That kind of puts things in perspective. Still a great improvement. Has it
been tested by how much the overall memory footprint of the JVM decreases
in larger benchmarks?

On Fri, 6 May 2022 at 23:28, charlie hunt <charlie.hunt at oracle.com> wrote:

> Hi Stefan,
>
> The graph Thomas shows in his blog is the GC part of the NMT output which
> does not include metadata.
>
> The GC part of NMT output includes native memory allocated on behalf of
> the GC itself such as a card table or remembered set .. those things that
> GC needs to do its work. The native memory allocated for the Java heap are
> in the "Java Heap" section of the NMT output. Class metadata is in the
> "Class" section of the NMT output.
>
> There is a "Native Memory Tracking Memory Categories" table that lists the
> sections / categories reported by NMT and a description of each at:
>
> https://docs.oracle.com/en/java/javase/17/troubleshoot/diagnostic-tools.html#GUID-5EF7BB07-C903-4EBD-A9C2-EC0E44048D37
>
> hths,
>
> Charlie
> On 5/6/22 2:13 PM, Stefan Reich wrote:
>
> I'm right now just trying to get over how amazing this graph is:
> https://tschatzl.github.io/2022/03/14/jdk18-g1-parallel-gc-changes.html
>
> 35-40% savings in memory use just by using JDK 18??? Who would have
> expected such a major improvement after 17 iterations of the language!
>
> Just so I'm sure I'm reading it correctly... the graph basically shows the
> Java heap's memory footprint in terms of committed native memory. Right?
>
> So it would include Eden, tenured generations, humongous objects, but not
> metadata and code. Is that correct?
>
> Basically tell me how much I should celebrate this. lol
>
> I did switch another small, pretty crammed (8 GB RAM) server over to JDK
> 18 and it does feel like there's a lot more memory available on it now and
> everything is a lot faster too.
>
> Cheers
> Stefan
>
> --
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>
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