At KVM Forum 2017 I gave a talk about the AioContext polling optimization that was merged in QEMU 2.9. It reduces latency for virtio-blk and virtio-scsi devices with the iothread= option on high IOPS devices like recent NVMe PCIe SSDs drives. It increases performance for latency-sensitive workloads and has been designed to avoid interfering with workloads that do not benefit from polling thanks to a self-tuning algorithm.
The video of the talk is now available:
The slides are available here (PDF).
