This Dagstuhl Seminar will convene researchers from diverse intellectual communities within computer science who share a common interest in software performance engineering (SPE) : making software run fast or otherwise consume few resources such as time, storage, energy, network bandwidth, etc. With the end of Moore’s Law and Dennard Scaling, microelectronic miniaturization is no longer increasing application performance. SPE has emerged as a promising and widely accessible way to improve performance, gaining increased attention across multiple research areas and industries. SPE encompasses the many ways of developing fast code for a wide range of applications and studying general methodologies and tools to improve and measure performance, including tailoring software to hardware features, algorithms, compiler technology, etc.