Optimising HLT code for run-time efficiency

An upgrade of the High level trigger (HLT) farm at LHCb will be inevitable due to the increase in luminosity at the LHC. The upgrade will be done in two main ways. The first way is to make the software more efficient and faster. The second way is to increase the number of servers in the farm. This paper will concern both of these two ways divided into three parts. The first part is about NUMA, modern servers are all built with NUMA so an upgrade of the HLT farm will consist of this new architecture. The present HLT farm servers consists of the architecture UMA. After several tests it turned out that the Intel-servers that was used for testing (having 2 nodes) had very little penalty when comparing the worst-case the optimal-case. The conclusions for Intel-servers are that the NUMA architecture doesn't affect the existing software negative. Several tests was done on an AMD-server having 8 nodes, and hence a more complicated structure. Non-optimal effects could be observed for this server and when comparing the worst-case with the optimal-case a big difference was found. So for the AMD-server the NUMA architecture can affect the existing software negative under certain circumstances. In the second part of the paper a program was made in order to help programmers find bottlenecks, optimize code and still maintain correctness. In the third part, the program from part two was used to optimize a bottleneck in the HLT software. This o ptimization gained around 1-10% in speed for suitable test-data.