On 7/28/10 11:31 AM, Stefan Seelmann wrote:
I was thinking lately about the DN class. I know that OpenDS (and probably
UnboundId, but not sure) has a DN.valueOf( "<a DN>" ) factory that returns a
DN potentially leveraging a cache associated to a ThreadLocal.
...
I don't think it's such a good idea :
- first, as it's ThreadLocal based, you will have as many cache as you have
threads processing requests. Not sure it competes with a unique cache, not
sure either we can't use the memory in a better way...
An advantage to use ThreadLocal is that you don't need to synchronize
access to the cache Could be worth to measure the performance
Using ConcurrentHashMap should not be a major performance penalty. I
mean, it *will* be more costly than not having any synchronization but
it sounds acceptable.
Another possibility is to use a CopyOnWriteArraySet, but I'm afraid that
it will crawl if many new DN are added.
difference, I wonder if the OpenDS team did some performance analysis?
They compared the performances they get with a ThreadLocal cache and no
cache : the gain was sensible (I don't have the number for OpenDS). FYI,
the DN parsing count for more or less 13% of the whole CPU needed
internally (network excluded) to process a simple search, and
normalization cost an extra 10%. There is most certainly a net potential
gain to implement a DN cache !
--
Regards,
Cordialement,
Emmanuel Lécharny
www.iktek.com
