Optimizing existing large codebase Measuring our software Many parameters can be measured o overall timing o memory usage and cache efficiency CPU efficiency (Cycles per instructions,vectorization level) level of parallelism,usage of the different cores I/O limitations if any For each of them,you need both overall data and detailed split per code unit o per item,per core and full machine measurement perf tools bottlenecks 8/57 S.Ponce-CERNOptimizing existing large codebase 8 / 57 S. Ponce - CERN Measure Modernize Mem threads low level c/c perf tools bottlenecks Measuring our software Many parameters can be measured overall timing memory usage and cache efficiency CPU efficiency (Cycles per instructions, vectorization level) level of parallelism, usage of the different cores I/O limitations if any For each of them, you need both overall data and detailed split per code unit per item, per core and full machine measurement