A number of recent Linux driver patches has reportedly resulted in significant performance gains for the Steam Deck. Valve’s handheld runs on the Linux-based SteamOS, and these patches can apparently improve the Steam Deck’s 1% low frame rates by as much as 31%.
A fresh ‘epp_boost’ feature for the AMD P-State driver is largely responsible for the performance boost. David Vernet, a Linux kernel hacker at Meta, is the developer behind it. The feature implements per-core Energy Performance Preference (EPP) for AMD CPUs. As far as I know, it’s not yet been reviewed by AMD’s Linux kernel engineers, though Vernet explains via the Linux kernel mailing list that it was developed with gaming specifically in mind (via Phoronix).
Vernet offers a technical breakdown of the inefficiency these patches are designed to address, writing, “In active (EPP) mode the platform autonomously picks the operating point between min_perf and max_perf, biased by the EPP hint, and the kernel only rewrites the CPPC request on policy or limit changes. A workload dominated by one mostly-busy thread that takes frequent short sleeps (common in gaming workloads, for example) can fare poorly under this strategy.”
He elaborates, “Each sleep decays the hardware’s performance signal, causing post-wakeup bursts to start at a low operating point and inflating tail latency even though the CPU is essentially fully busy while work is available,” going on to add, “A game’s main or render thread typically blocks briefly on a futex or a GPU fence every frame, and the resulting frequency droop shows up directly as stale frames and inflated frame-time percentiles.”