Linux Proposes “Modern Standby” Rival with New Runtime ABI

The Linux kernel community is actively developing a new Runtime ABI (Application Binary Interface) designed to offer a robust alternative to the “Modern Standby” power state found in Windows. This initiative aims to provide a more reliable and transparent low-power idle mode for laptops and other mobile devices, addressing long-standing frustrations with the existing suspend-to-idle (s2idle) framework. The goal is to deliver better battery life predictability and system responsiveness without the pitfalls associated with Microsoft’s implementation.

For years, Linux users, particularly on laptops, have grappled with inconsistent power management during sleep states. The current default, s2idle, often fails to achieve significant power savings because numerous system components remain partially active. In contrast, the deeper suspend-to-RAM (S3) state is highly efficient but is frequently unavailable on modern hardware, as many OEMs design their systems around Windows Modern Standby. This Microsoft technology, known as S0ix low-power idle, promises instant wake-ups and background activity like receiving notifications but has been widely criticized for causing excessive battery drain and unexpected heat generation when systems fail to enter a truly low-power state.

The proposed Linux solution involves creating a well-defined Runtime ABI. This interface would allow device drivers to expose their low-power capabilities to the kernel’s power management core in a standardized way. The core idea is to move beyond the current model where the kernel makes assumptions about device states. Instead, drivers would explicitly declare when their devices are ready for a low-power idle mode and handle the necessary transitions. This shift promises greater consistency and control, enabling the kernel to aggregate readiness from all drivers and confidently place the entire system into a genuine, power-saving idle state.

Driver cooperation is essential for this new ABI to succeed. Each hardware driver must be updated to support the interface, reporting its idle constraints and managing its power rails appropriately. The development effort is substantial, as it requires changes across the driver ecosystem. However, the potential payoff is significant: a standardized, cross-platform framework that could work reliably on any compatible hardware, from x86 systems with Intel/AMD chips to ARM-based devices. This would decouple Linux from the opaque firmware implementations often tied to Windows-specific power models.

Early code has already been submitted to the Linux kernel mailing list, sparking discussion among maintainers. The proposal is not about replicating Modern Standby’s model of allowing background tasks. Instead, the focus is squarely on achieving a predictable and deep low-power idle that prioritizes battery conservation. The system would wake only for critical interrupts, similar to a traditional sleep state, but with the faster resume times associated with a shallow idle. This approach directly tackles the core complaint about Modern Standby, uncontrollable power drain, by design.

If widely adopted, this Runtime ABI could fundamentally improve the out-of-the-box experience for Linux on laptops. It represents a strategic move to solve a persistent hardware compatibility issue through software standardization. While the rollout will depend on driver updates and hardware enablement, the project signals a major step toward closing the power management gap with proprietary operating systems and providing users with a dependable, efficient sleep state.

(Source: Phoronix)