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.”
Vernet writes that the most obvious fix would have been to globally force “EPP=performance” but this would not have been power efficient—especially for handhelds like the Steam Deck. So, instead these patches introduce “an opt-in, per-core EPP boost.” From there, Vernet offers a breakdown of technical precedents, his testing methodology, and how the fix works in specific detail but honestly I’ve barely been keeping up with all the Linux riddling to this point. For those who reckon they’ll fare better than me, you can read the message archive here.
I’ve not had a chance to check out the patch myself, but Phoronix took a look using the Civilization VI game benchmark. Their testing apparently saw the 1%-low fps pick up by 31.8%, and frame time improve by 4.1%. That’s not nothing for Valve’s years old handheld, though newer AMD Ryzen systems would likely also benefit.
Mind you, that’s only so long as you don’t mind a spot of noodling in Linux’s guts to activate the epp_boost feature after downloading the patch. To get the most out of the patch, you’ll need to set ‘amd_pstate.epp_boost=1’. After that, ‘/sys/module/amd_pstate/parameters/epp_boost’ can be used to check whether the feature is active. I know I said handhelds are cooked, but I will still gladly take any performance boost offered to my wizened Steam Deck.