Re: MemPools rewrite

 both current and proposed memPools keep track of freelist with an
 array of pointers. I guess this is done to increase the speed of
 allocs/frees, but has quite large memory overhead for allocation
 sizes comparable to size of pointer. On 64-bit systems pointers
 are 8-bytes...

 In chunked design, it is possible to keep track of freelist with
 bit-arrays. Because freed ptr location within Chunk can be
 calculated from Chunk start, ptr and object size, its index into
 Chunk can be used to set/clear a bit of the freelist. (could also
 be used to assert that same object is not freed twice)

 This could reduce allocation memory overhead of chunked design to
 1 bit per object. But would need to search bitarray for a free
 object at Alloc time. A scan of bit-array of 1024 items in steps
 of 4-byte int comparisons can take a max of 32 comparisons before
 free item is reliably found. Full chunks can be skipped by tracking
 used-count of a chunk.

 Is such overhead prohibitively expensive?
 What should be our priority, reducing memory overhead or reducing
 CPU overhead?

------------------------------------
 Andres Kroonmaa <andre@online.ee>
 Delfi Online
 Tel: 6501 731, Fax: 6501 708
 Pärnu mnt. 158, Tallinn,
 11317 Estonia
Received on Thu Oct 19 2000 - 02:20:12 MDT