Re: Reducing the chunk header sizes on all memory context types

Got it: sizeof(SlabBlock) isn't a multiple of MAXALIGN,

(gdb) p sizeof(SlabBlock)
$4 = 20

but this coding requires it to be:

#define SlabBlockGetChunk(slab, block, idx) \
    ((MemoryChunk *) ((char *) (block) + sizeof(SlabBlock)    \
                    + (idx * slab->fullChunkSize)))

So what you actually need to do is add some alignment padding to
SlabBlock.  I'd suggest reverting df0f4feef as it seems to be
a red herring.

            regards, tom lane