Is It Possible to Allocate Contiguous Physical Memory from Userspace in Linux? Guaranteed Pages Beyond Huge Pages
Introduction
In the Linux ecosystem, memory management is a complex dance between flexibility, performance, and hardware constraints. For most applications, the kernel’s abstraction of virtual memory—where contiguous virtual addresses mask fragmented physical memory—works seamlessly. However, certain use cases demand contiguous physical memory: direct memory access (DMA) for hardware devices, real-time systems with strict latency requirements, or high-throughput data processing where even huge pages may not suffice.
A common misconception is that userspace applications can directly request contiguous physical memory. In reality, Linux’s design prioritizes dynamic memory allocation and fragmentation tolerance, making such guarantees elusive. This blog explores whether userspace can allocate guaranteed contiguous physical memory, beyond the limitations of huge pages, and what workarounds exist today.