NMT and os::split_reserved_memory?

[Thomas Stüfe]

Hi Zhengyu,

thank you! That is unfortunate, but I'll see what I can do.

Cheers, Thomas

On Thu, Apr 23, 2020 at 5:51 PM Zhengyu Gu <zgu at redhat.com> wrote:

> Hi Thomas,
>
> On 4/23/20 10:05 AM, Thomas Stüfe wrote:
> > Hi,
> >
> > How does NMT handle os::split_reserved_memory?
>
> I don't think NMT handles it.
>
> >
> > Lets say I reserve a space, then split it into two spaces
> > using os::split_reserved_memory() (which really is a noop for most
> > platforms). Then I want to set both spaces to different flags.
>
> You can remove the whole region, then create two separate regions.
> The intricate part is when the region contains committed regions, I am
> not so sure how virtual memory system behaves.
>
> Thanks,
>
> -Zhengyu
>
> >
> > Setting the second one triggers an assert: assert(reserved_rgn->flag() ==
> > mtNone, "Overwrite memory type");
> >
> > since I assume NMT is not aware that splitting happened.
> >
> > What would be the correct way to go here? Can I somehow inform NMT that
> > this region has been split? I assume within NMT both split regions are
> > still represented by one reserved_rgn object.
> >
> > Thank you,
> >
> > Thomas
> >
>
>