The intention of this page is to present experiments with non-CRUD data operations.
An aggregation operations adds up the values of a number of objects. When executing such an operation in RAMCloud three questions, among others, are of interest:
The experiments below are centered around the question about where to execute the operation. Three different scenarios are implemented:
for(uint64_t i = 0; i < range; ++i) { LogEntryHandle handle = objectMap.lookup(tableId, i); const Object* obj = handle->userData<Object>(); int *p; p = (int*) obj->data; sum += (uint64_t)*p; } |
/** * 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; } |
//** * Aggregation via traversing all SegmentEntries throughout the entire Log */ uint64_t Log::aggregate() { uint64_t sum = 0; //Iterate over all Segments in the Log foreach (ActiveIdMap::value_type& idSegmentPair, activeIdMap) { Segment* segment = idSegmentPair.second; //Iterate over all SegmentEntries in a Segment for (SegmentIterator i(segment); !i.isDone(); i.next()) { SegmentEntryHandle seh = i.getHandle(); //Check that it is an Object if (seh->type()==560620143) { const Object* obj = seh->userData<Object>(); int *p; p = (int*) obj->data; sum += *p; } } } return sum; } |
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:
#number of objects |
client-side aggregation |
server-side aggregation |
server-side aggregation |
server-side aggregation |
---|---|---|---|---|
10.000 |
63 ms |
1 ms |
74 ms |
6 ms |
100.000 |
648 ms |
12 ms |
84 ms |
9 ms |
1.000.000 |
6485 ms |
127 ms |
168 ms |
21 ms |
10.000.000 |
64258 ms |
1378 ms |
781 ms |
142 ms |
100.000.000 |
652201 ms |
19854 ms |
6245 ms |
1422 ms |