Hi Maxim,
I implement a new version of cuckoo hash based on the ODP buffer/pool.
As I’ve mentioned earlier, the use of ring in cuckoo hash is like to
the use of
a container, e.g. a queue in C++ STL. In current ODP implementation, I found
that
the ODP queue is implemented more likely a facility for transmitting objects,
not
a container to store objects. Look at the ODP queue enqueue interface:
int odp_queue_enq(odp_queue_t queue, odp_event_t ev);
the *odp_event_t* is related to the events, but I only want to use odp_queue to
storing and retrieving objects, any objects.
So I use ODP buffer/pool interfaces instead of ODP queue
for the new cuckoo hash implementation.
However, compared to the previous implementation based on ring, this
version
suffers a serious performance degradation. The evaluation is carried out on a
Intel
servers. I test lookup time for 1000 lookups on a table storing 1 million
items.
The ODP buffer/pool version suffers at least a 2x performance degradation.
This is the buffer/pool version, for 1M insert, and 1000 lookup time:
Average insert time = 2.383836, lookup time = 0.000353,
This is the ring version.
Average insert time = 1.629115, lookup time = 0.000098
This performance degradation stems from the heavy implementation of
ODP buffer/pool. In the ring based one, all the key is stored in a big array,
and
the ring only stores the array indexes of each key. Keys are retrieved using
array indexes.
In the new one, I use ODP buffer to store the key content. Keys are retrieved
by
dereferencing a *odp_buffer_t* handle.
With this high performance degradation, I suggest moving ring into the
odp/api
as a container implementation, and use the previous implementation of cuckoo
hash.
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