Why different default values for MetaspaceSize?

[Thomas Stüfe]

Thank you, Coleen and Stefan!

On Wed, Feb 17, 2021, 15:56 Coleen Phillimore <coleen.phillimore at oracle.com>
wrote:

>
>
> On 2/17/21 8:08 AM, Thomas Stüfe wrote:
> > Hi,
> >
> > Does anyone know why the default for MetaspaceSize (the initial threshold
> > which triggers the first metaspace-motivated GC) is cpu- and
> > compiler-tier-dependent?
> >
> > IIUC this has been the way since PermGen removal.
>
> The MetaspaceSize option came from PermSize which was platform
> dependent.  I don't think it needs to be like that now.
> Some configurations may way to ergonomically set MetaspaceSize larger to
> prevent early GCs but that shouldn't be platform dependent.
> The ScaleForWordSize is a macro that increases the size for 64 bits.
> I'm not sure if that's still needed but that should cover any 32/64 bit
> dependencies on the size you pick as the default (between 16 and 12M).
> Thanks to StefanK for consultation.
>
> Coleen
>
>
> >
> > I can see a vague connection between compiler tier and this size since
> > MethodCounters live in metaspace and we probably have more of them with
> C2?
> > I'm guessing here. But the size difference is not large at all (16m vs
> 12m)
> > and probably does not make a big difference. Why not just set it to one
> > default size?
> >
> > Thanks, Thomas
>
>