[dmd-internals] Giving better static data limits to the GC

[Leandro Lucarella]

Walter Bright, el 22 de agosto a las 12:25 me escribiste:
>  I know this is probably really low priority for DMD, but any answer
>  would be appreciated, even if it is something like "no idea how doable
>  it is, it would take time to think about it and is low priority" :)
> 
> 
>    I don't think spending a lot of effort on the static data is worthwhile,
>    as very little of modern programs should consist of static mutable data.
> 
>    What's held me back from adding in precise scanning data for everything is
>    the large expansion of the memory footprint of a program to hold all this
>    data.

Thanks for the answer. My experiments show that static data is relevant.
Comparing 2 GC implementations, one with very few types (druntime
implementation) and another using a few more types, including a couple
of templates, the second is measurably slower. The types generates
a *lot* of rw static data.

Even when I agree that it might be too much to add type information to
the static data, grouping only the static data that should be scanned
(i.e. D-only global variables, and leaving out all the
TypeInfo/ClassInfo) can make a big difference.

Would that be too hard?

Right now I'm under the serious dilemma of whether I should got back to
the more messy way of coding (with few types) or pay the price, which is
a very hard decision because I don't want to make the code uglier but
I don't want to have a slower GC either.

Thanks.

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Leandro Lucarella (AKA luca)                     http://llucax.com.ar/
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