using skiplist for quotas.db

[Ken Murchison]

Rob Mueller wrote:
> 
>> so I wonder, will skiplist be a better choice?  obviously running
>> quota(8) will be a very cheap operation, but I'm worried about
>> contention on the quota database during delivery etc.  (these users are
>> for the most part not actively using the system -- they get less than
>> one message per day each(!) -- so I probably worry too much.)
> 
> The problem I saw was that accessing a skiplist db involves locking the 
> entire file I believe. This felt like a huge point of contention, 
> especially since every email delivered would lock it. I never did end up 
> trying it out to test that though, so I wouldn't quote me on that, Ken 
> could confirm.

This is true.  If you want to use a single database, I would consider 
using BDB (as painful as it sounds), since it does localized locking.  I 
don't believe that either choice has been tested thoroughly however.

-- 
Kenneth Murchison
Systems Programmer
Project Cyrus Developer/Maintainer
Carnegie Mellon University