PBC, Const Tables, and STRINGs

[Andrew Whitworth]

What Sub metadata are you talking about that isn't stored in the
constant tables? Where is this data stored, if not in the constant
tables?

--Andrew Whitworth



On Sun, Apr 25, 2010 at 8:16 PM, chromatic <chromatic at wgz.org> wrote:
> The current version of PBC uses constant tables for PIR artifacts such as
> literal strings in PIR.
>
> It doesn't use constant tables for data such as Sub metadata.  While NQP can
> generate closures and inner blocks fairly efficiently, we have to keep extra
> constant STRINGs around in the system because our freeze/thaw mechanism
> doesn't know how to store constant attributes of Subs in the packfile constant
> tables.
>
> We could reduce PBC size, fakecutable size, freezing time, thawing time, and
> runtime memory use (not to mention GC runs) by coalescing these attributes
> into PBC constants somehow.
>
> Rough figures on Rakudo startup show some 405,000 STRINGs thawed from PBC,
> while some 16,000 are unique.  That's 95% waste.
>
> Perhaps the ImageIO PMC's shift/unshift string VTABLEs could manage these
> constant STRINGs appropriately.
>
> -- c
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