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Re: GUILE GC -- Write barrier for vectors

From: Han-Wen Nienhuys
Subject: Re: GUILE GC -- Write barrier for vectors
Date: Tue, 16 Jul 2002 11:22:41 +0200

address@hidden writes:
> I'm reading the patent (gosh, what verbosity) -- but interestingly,
> the claim is only made for not copying entire pages (cards in Scheme
> terms), that are marked conservatively. If you one uses a second set
> of mark bits, you could leave alone exactly those objects that are
> marked conservatively (iso. the whole page). The price is that you
> have another mark-bit vector (1.5 % memory overhead), that the free
> space in the conservatively marked pages is fragmented, and that there
> is more overhead (checking the marked-conservatively-bit) during the
> copy phase.

Actually, I can top that. If you store the range of cells that is
marked conservatively, you can still beat the patent but avoid the 2nd
bitvector overhead. All this (bitvector ptr, conservative-cell range,
generation count and card) flags could even be stored in the 1st
header cell.


Han-Wen Nienhuys   |   address@hidden    |

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