Can we conclude this discussion? In summary:
* The current comparison function causes bad IO patterns for iterate on
the dspace db. We can change it but the disk format will change in new
releases.
- If we change it, either we check a version number and provide the
right comparison function, or we perform migration to the new storage
format.
- If we don't change it, we can still improve performance by
iterating from the last entry to the first, but we can't use
DB_MULTIPLE_KEY, which also improves performance for big filesystems.
I don't really have a preference either way.
* If we change PVFS_ds_position from uint32_t to uint64_t, we can use
the handle as the position, and avoid opening the dspace db with the
RECNO flag, which is killing our performance on writes.
I think this sounds good too. We would be happy to help test any
combination of the options you list.
-Phil
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