Timothy Arceri at Valve is still working on the on-disk Mesa shader cache even though the GLSL/TGSI shader cache and RadeonSI binary caches have landed. In particular, his recent effort has been about improving the cold performance — or when there isn’t a shader cache present or it needs to be re-generated…

Source: Phoronix – Arceri Is Working To Further Improve Mesa’s Shader Cache Startup Performance