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/**
* Aggregation Callback
*/
void
aggregateCallback(LogEntryHandle handle, uint8_t type,
                      void *cookie)
{
        const Object* obj = handle->userData<Object>();
        MasterServer *server = reinterpret_cast<MasterServer*>(cookie);

        int *p;
        p = (int*) obj->data;
        server->sum += (uint64_t)*p;
}

Benchmarking

The benchmarks below have been executed using a separate server for client and server connected via Infiniband. After each run, the equality of the client-side and server-side calculated sum has been checked. The benchmarks allow the following conclusions:

• By executing the aggregation on the server-side a performance improvement up to a factor of 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).
• Invoking the hashTable forEach method comes at a penalty of around 200 ms (presumably to due the Callback).
• 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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