The Linux Storage, Filesystem & Memory Management Summit gathers the top development, research experts and subsystem maintainers to map out and implement improvements to the Linux filesystem, storage and memory management subsystems.
ORBIT partner Andrea Arcangeli from Red Hat presents „userfaultfd“ (more about the programme).
What is userfaultfd?
userfaultfd is allowing to manage memory at the pagetable level. This is done by delivering the page fault notification to userland to handle it with proper userfaultfd commands. These commands mangle the address space, without involving heavyweight structures like vmas.
The primary motivation of this work is KVM postcopy live migration (one form of cloud memory externalization).
Glossar (by Wikpedia)
Page table is the data structure used by a virtual memory system in a computer operating system to store the mapping between virtual addresses and physical addresses. Virtual addresses are used by the accessing process, while physical addresses are used by the hardware.
A page fault is a type of interrupt, called trap, raised by the hardware when a running program accesses a memory page that is mapped into the virtual address space, but not loaded in physical memory.
A modern computer operating system usually segregates virtual memory into kernel space and user space, aka userland. This separation primarily serves to protect data and functionality from faults and malicious behaviour.
VMA means vSphere Management Assistant, which is a virtual machine that includes prepackaged software such as a Linux distribution (…). Source
With Live Migration a running virtual machine or application is moved between different physical machines without disconnecting the client or application. Memory, storage, and network connectivity of the virtual machine are transferred from the original host machine to the destination.
Post-copy migration is a way of moving a media item – or more general: data – from one virtual server to another one with minimal or zero interruption for the user (for more info, watch demo on post-copy migration on ORBIT).
KVM (Kernel-based Virtual Machine) is a virtualization infrastructure for the Linux kernel.


