A few pages that describe optimisation and profiling of code:

 * https://twiki.cern.ch/twiki/bin/view/LHCb/CodeAnalysisTools#Code_Profiling
 * https://twiki.cern.ch/twiki/bin/viewauth/Atlas/OptimisingCode
 * http://atlas-computing.web.cern.ch/atlas-computing/links/nightlyDocDirectory/Valkyrie/html/