[Gc] bottom_index

Boehm, Hans hans.boehm at hp.com
Thu Nov 18 11:39:03 PST 2004


It's used by GC_apply_to_all_blocks, which is used for
initiating the heap sweep after marking, and by the
incremental GC for marking, and in a few other places
that need to walk all blocks in the heap.

IIRC, it's also useful for hiding the data structure differences
between 32 and 64-bit machines.  This code no longer needs to
know whether the top level of the tree is really a hash table.

Hans 

> -----Original Message-----
> From: gc-bounces at napali.hpl.hp.com
> [mailto:gc-bounces at napali.hpl.hp.com]On Behalf Of Hans Van den Eynden
> Sent: Tuesday, November 16, 2004 12:06 AM
> To: garbage collector
> Subject: [Gc] bottom_index
> 
> 
> On tree.html there is:
> 
> "Bottom_index structures contain slightly more information 
> than just hdr 
> pointers. The asc_link field is used to link all bottom_index 
> structures 
> in ascending order for fast traversal. This list is pointed to be 
> GC_all_bottom_indices. It is maintained with the aid of key 
> field that 
> contains the high bits corresponding to the bottom_index."
> 
> 
> What do you mean by 'fast traversal'? For what purpose will the gc 
> traverse the bottom_index structures one by one??
> 
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