Older blog entries for mulix (starting at number 250)

Scalable I/O paper online

Our new paper is online: "Scalable I/O---A Well-Architected Way to Do Scalable, Secure and Virtualized I/O", by Julian Satran, Leah Shalev, Muli Ben-Yehuda, and Zorik Machulsky. This is an overview paper showcasing the main ideas underlying a system we've been working on on and off since 2004. It's not as detailed as I would've liked due to the space constraints, but hopefully it will be followed by more detailed papers. The slides I'll be presenting later today at WIOV '08 are also available and go into a bit more details in areas.

Today in both virtualized and non-virtualized systems the entire I/O functionality is based on device drivers. They are central to any system structure; both anecdotal and informed evidence indicates device drivers as a major source of trouble in the classical OS and a source of scaling and performance issues in virtual I/O, due to "trusted intermediary" required for the shared I/O. We propose an architecture which virtualizes the entire I/O subsystem rather than each I/O device, and provides device-independent I/O at higher level of abstraction than the traditional I/O interfaces. In our suggested architecture the system robustness is increased by isolating drivers; efficient and scalable virtualization becomes possible by a complete separation of the I/O and compute function and introducing a protection model that does not require a trusted intermediary for I/O.

Syndicated 2008-12-10 19:18:25 from Muli Ben-Yehuda

new IOMMU paper available

New online for your perusing pleasure: "Direct Device Assignment for Untrusted Fully-Virtualized Virtual Machines", by Ben-Ami Yassour, Muli Ben-Yehuda and Orit Wasserman, IBM Research Report H-0263.

This is a short paper describing and evaluating our work earlier this year on direct device assignment in KVM, using Intel's VT-d IOMMU. Not much new here if you've read our other IOMMU papers, but it does make two contributions. First, it's the best (and only) available description (IMHO) of KVM's direct device assignment code, and second it's yet another data point on the relative performance of device emulation vs. virtual I/O drivers vs. direct device assignment. As always, comments appreciated. The abstract follows.

The I/O interfaces between a host platform and a guest virtual machine take one of three forms: either the hypervisor provides the guest with emulation of hardware devices, or the hypervisor provides virtual I/O drivers, or the hypervisor assigns a selected subset of the host's real I/O devices directly to the guest. Each method has advantages and disadvantages, but letting VMs access devices directly has a number of particularly interesting benefits, such as not requiring any guest VM changes and in theory providing near-native performance.

In an effort to quantify the benefits of direct device access, we have implemented direct device assignment for untrusted, fully-virtualized virtual machines in the Linux/KVM environment using Intel's VT-d IOMMU. Our implementation required no guest OS changes and---unlike alternative I/O virtualization approaches---provided near native I/O performance. In particular, a quantitative comparison of network performance on a 1GbE network shows that with large-enough messages direct device access throughput is statistically indistinguishable from native, albeit with CPU utilization that is slightly higher.

Syndicated 2008-11-24 18:35:51 from Muli Ben-Yehuda

notes for Sunday Oct 20 through Tuesday Oct 22nd

This is not serious, I'm supposed to remember what I was doing three days ago? I can barely remember what I had for breakfast this morning.

I started walking again in the mornings. Today I was up before the crack of dawn for a brisk walk on the sea shore, and when I got back home, I even had enough energy left for a few rounds with the boxing bag. Finished reading Haruki Murakami, and now re-reading Living the Martial Way. It's a funny little book, so earnest it's hard to take it seriously, but with nuggets of wisdom nonetheless.

Syndicated 2008-10-22 09:52:51 from Muli Ben-Yehuda

The WIOV 08 website is up, including the full program! See y'all there.

Syndicated 2008-10-19 07:27:44 from Muli Ben-Yehuda

notes for Thursday Oct 16 through Saturday Oct 18

Thursday: just another day at work . In the afternoon, went to meet an amazing carpenter (US: cabinet maker). Spent three hours going over the plans in minute detail, making lots of changes, and then he told us how much it was going to cost. Staggered to Noga's cauldron for a late dinner.

Friday: BBQ with old friends at Ira's. Once upon a time it would've been all Linux hacking, all the time, but now business and what the kids are doing is that much more interesting. Progress, of a sort.

Saturday: a day of rest and recuperation. In the evening off to Mika's 1-year old birthday party. I still remember the sense of accomplishment we felt at Yael's 1-year old birthday party, that we actually managed to raise her and she is fine. Resumed reading Haruki Murakmi's What I Talk About When I Talk About Running.

Syndicated 2008-10-19 07:25:11 from Muli Ben-Yehuda

notes for Wednesday Oct 15

A day of odds and ends. The WIOV schedule should be going up today or tomorrow. Continued looking into the feasibility of a new project which will require coordination with an inordinate amount of people. Worked on a bunch of new patent disclosures. Hacked a bit on a new idea for IOTLB design until the serial port server stopped giving me love, and then went into paper reading mode.

Syndicated 2008-10-16 09:36:47 from Muli Ben-Yehuda

Reservoir research report available

Last year I helped conceive and write a proposal for an ambitious EU project called Reservoir: Resources and Services Virtualization without Barriers. IBM Research Report H-262, 2008, "RESERVOIR---An ICT Infrastructure for Reliable and Effective Delivery of Services as Utilities" is now available. This research report summarizes the (172 pages...) proposal and describes the key ideas underlying Reservoir.

Syndicated 2008-10-15 09:12:03 from Muli Ben-Yehuda

notes for Tuesday Oct 14

Lunch with the Tel-Aviv, business oriented, brunch of the family in their nice new house. In the evening didn't feel like doing much of anything; ended up de-cluttering my publications page.

Syndicated 2008-10-15 09:05:10 from Muli Ben-Yehuda

notes for Monday Oct 13

More work on the nap and vnic papers in the morning, making progress toward their respective deadlines. In the evening BBQ---fillet mignon and a good wine---with my folks in our garden.

Syndicated 2008-10-14 07:46:10 from Muli Ben-Yehuda

notes for Sunday Oct 12

Woke up bleary eyed, but settled into a productive day at the office debugging by proxy and reviewing a couple of draft papers (vnic and nap). In the evening got some work done on the secret project, too.

Syndicated 2008-10-12 19:41:46 from Muli Ben-Yehuda

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