Speakers
Description
The current Linux memory management framework lacks the mechanism for tracking IOMMU page table (IOPT) consumption across sparse virtualization workloads. By utilizing the IOMMUFD and VFIO frameworks, hypervisors dynamically map and unmap massive IOVA regions, often leaving intermediate page table directories stranded and invisible to the core kernel. This session talks about the current state of IOPT observability and attempts to propose new features and enhancements for IOPT memory reclamation.
The session proposes a design for an IOMMU Page Table Shrinker that allows lockless and lazy reclamation of stranded IOPT memory, specifically by the intermediate tables while employing the generic_pt to keep the shrinker arch-agnostic. We invite a discussion to explore strategies for lockless tracking, page table branch severance, and lifecycle management using RCU state machines to ensure that the core kernel can harvest stranded memory under pressure without penalizing the IOMMU mapping paths.