RFR (S): 6490394: G1: Allow heap shrinking / memory unmapping after reclaiming regions during Remark

[Ruslan Synytsky]

Hi Thomas,

On Tue, 11 Dec 2018 at 10:42, Thomas Schatzl <thomas.schatzl at oracle.com>
wrote:

> Hi Ruslan,
>
> On Mon, 2018-12-10 at 18:43 +0100, Ruslan Synytsky wrote:
> >
> > On Mon, 10 Dec 2018 at 16:48, Thomas Schatzl <
> > thomas.schatzl at oracle.com> wrote:
> > > Hi,
> > >
> > >   see inline.
> > >
> > > On Mon, 2018-12-10 at 16:22 +0100, Ruslan Synytsky wrote:
> > > > Dear Thomas and Sangheon, hope you are doing great.
> > > >
> > > > I just noticed an important improvement related to vertical
> > > > scaling and would like to clarify details mentioned in the
> > > > release notes
> > > >
> >   [...]
> > > > > This behavior may be disabled by changing minimum Java heap
> > > > > size via the -Xms option.
> > > > At the same time if a user adjusts Xms option then he/she does
> > > > not get this "smart behaviour" at all.
> > > >
> > >
> > > This sentence should indicate that you can disable giving back
> > > memory to the OS by modifying the Xms value. In particular, setting
> > > the Xms to the Xmx value - which is a rule that is part of the
> > > default heap sizing policy.
> >
> > Then I think the wording in the release notes is confusing as there
> > is only one case when changing Xms disables giving memory back,
> > specifically when Xms = Xmx.
>
> The behavior with Xms = Xmx corresponds to normal heap sizing
> heuristics.
>
> What would you prefer? Something like:
>
> "This behavior may be disabled in accordance with default heap sizing
> policies by setting minimum Java heap size to maximum Java heap size
> via the -Xms option."
>
Yes, something like this sounds much better.

Or just delete this sentence, as this behavior is part of default Java
> heap sizing policies anyway?

I believe it's good to keep the description.

Thanks


> > > > Are these rephrased statements correct?
> > >
> > > Almost :) Corrections above.
> > >
> > > Note that the implementation of JEP 346 has been pushed today, so
> > > it will be JDK12 no matter what - there is only some post-push JEP
> > > work to do.
> >
> > It's great! I will run some tests on my side later this week.
>
> Looking forward to your results.
>
> Thomas
>
>
>

-- 
Ruslan
CEO @ Jelastic <https://jelastic.com/>
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