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Friday, October 27 • 3:45pm - 4:15pm
Applying Polling Techniques to QEMU: Reducing virtio-blk I/O Latency - Stefan Hajnoczi, Red Hat, Inc.

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Polling was recently merged in QEMU to improve disk I/O performance on high IOPS devices like NVMe drives. Notification latency has become a significant factor in the total request time because these devices complete I/O so quickly. Polling allows QEMU to skip notifications, thereby reducing latency.

This talk explains the pros and cons of polling and how a self-tuning algorithm can adapt for best results with each workload. The state of userspace polling is examined and how various event sources like sockets, timers, and BHs can be incorporated.

This talks covers the interaction between device emulation and the event loop, and how this affects I/O performance. By understanding how polling works with virtio-blk it is possible to consider the technique for other devices in the future.


Stefan Hajnoczi

Principal Software Engineer, Red Hat, Inc.
Stefan works on open source virtualization in Red Hat's KVM team. He has contributed to QEMU since 2010 with a focus on the block layer and tracing. Stefan is a member of the QEMU Leadership Committee which represents the project with Software Freedom Conservancy. He also acts as... Read More →

Friday October 27, 2017 3:45pm - 4:15pm
Hilton Grand Ballroom
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Attendees (11)