Performance of the ATLAS High Level Trigger in the 2011 and 2012 run

The ATLAS detector operated during the last 3 years in the LHC beam line, collecting more than 27 fb^-1 of proton-proton events. This allowed researchers to detect a new boson, compatible in many of its properties with the long sought Higgs Boson. One of the main ATLAS components is its complex calorimeter system. This sub-detector is able to detect many of the fundamental processes involved in the physics search. For instance, photon, electron, taus and jets candidates detection as well as missing transverse energy measurement are per- formed using calorimetric information. The calorimeter also plays a central role in the ATLAS trigger system, helping to reduce the large amount of input events (order of 20-30 millions of events per second) to a manageable rate (few hundreds of events per second) recorded for more detailed physics analysis. The trigger system is divided in three levels, the first one implemented in electronic boards and the other two with programs running on a dedicated computing cluster interfaced with the detector electronics. The presentation describes the performance of the tau, jet and missing transverse energy trigger in 2011 and 2012 together with the improvements made to cope with increased luminosity and pile-up conditions