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The benchmarks below have been executed using separate machines (out of the Stanford RAMCloud cluster) for client and server which are connected via Infiniband. After each run, the equality of the client-side and server-side calculated sum has been checked. During all runs, the hash table size was set to 5GB This particular benchmark allows the following conclusions:
- By executing the aggregation on the server-side a performance improvement up to a factor 50 can be seen.
- When traversing a set of distinct objects, retrieving a single object takes about 7-8?s (or a RAMCloud client can request about 130.000 objects/sec from a single RAMCloud server).
- When invoking the hashTable forEach method the whole allocated memory for the hashtable has to be traversed. This is fine if the hashtable is densely packed with objects. In case of a sparse population with objects (as in the examples below, where the hashtable had a size of ~2.5GB and some experiments stored only a few objects ) this introduces a penalty.
- When traversing large amounts of objects the forEach method is 1.6-1.8x faster that looking up each individual object.
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