I/O virtualization enables time and space multiplexing of I/O devices, by mapping multiple logical I/O devices upon a smaller number of physical devices. However, due to the existence of additional virtualization layers, requesting an I/O from a guest virtual machine requires complicated sequences of operations. This leads to I/O performance losses, and makes precise timing of I/O operations unpredictable. This paper proposes a hardware I/O virtualization system, termed the Virtualized Complicated Device Controller (VCDC). This I/O system allows user applications to access and operate I/O devices directly from guest VMs, and bypasses the guest OS, the Virtual Machine Monitor (VMM) and low layer I/O drivers. We show that the VCDC efficiently reduces the software overhead and enhances the I/O performance and timing predictability. Furthermore, VCDC also exhibits good scalability that can handle I/O requests from variable number of CPUs in a system.
@InProceedings{jiang_et_al:LIPIcs.ECRTS.2017.5, author = {Jiang, Zhe and Audsley, Neil}, title = {{VCDC: The Virtualized Complicated Device Controller}}, booktitle = {29th Euromicro Conference on Real-Time Systems (ECRTS 2017)}, pages = {5:1--5:20}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-037-8}, ISSN = {1868-8969}, year = {2017}, volume = {76}, editor = {Bertogna, Marko}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2017.5}, URN = {urn:nbn:de:0030-drops-71501}, doi = {10.4230/LIPIcs.ECRTS.2017.5}, annote = {Keywords: Many-core System, I/O Virtualization, Real-time I/O, Hardware Manager} }
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