Sharing the markword (aka Valhalla's markword use)

[David Holmes]

On 10/03/2024 1:38 pm, John Rose wrote:
> What Dan said.  Here’s more color commentary:
<snip>
> I suggest adding, to Klass itself, a field which is a prototype
> header for the object, with all the right bits in place ... 
> (I thought we already had something like this somewhere, but
> a quick check came up empty…)

We used to have the biased-locking prototype header.

klass.hpp
   // Biased locking support
   // Note: the prototype header is always set up to be at least the
   // prototype markOop. If biased locking is enabled it may further be
   // biasable and have an epoch.
   markOop prototype_header() const      { return _prototype_header; }

Cheers,
David