Fixing one issue sometimes brings another ten to the program. To detect these issues, especially performance issues, we often have to supply the program with input, that forces its worst-case behaviour. 
A popular solution to automatic inputs generation is so called fuzzing, however, its intention is to find functional bugs. In this work, we aim to construct an automatic generator of inputs whose task will be to trigger performance fluctuations. So we propose to tune fuzzing mutation rules and ways of processing the information about program run, to particularly trigger the performance bugs. We integrate our solution into a performance profile manager Perun, which stores information about every run as a profile and is able to compare these profiles to check for performance change. Therefore we can prove that executing with certain input takes more time or memory. We tested our fuzzer on several artificial projects, which shows its potential with generated inputs that prolong the runtime of the program. Such a solution would allow developers to regularly test every version of a project for performance bugs and avoid them completely by automatically finding new exhausting inputs before release.