Tim Deegan

Hello. Iʼm Tim Deegan, a computer scientist and coder, living in Cambridge, England. (If youʼre looking for the DJ or the weatherman, try elsewhere.)
My email address is tjd@phlegethon.org.
I blog occasionally.


Iʼm a systems programmer at Coho Data, working on the lowest levels of their storage stack. I mostly work in C on linux, with occasional bits of assembler and kernel programming. Itʼs interesting work, full of distributed and concurrent systems problems and performance optimizations. If thatʼs your idea of fun too, get in touch – we have engineering offices in Vancouver (Canada) and Cambridge (UK).

I worked on the Xen hypervisor for nine years, at XenSource and Citrix. Most of my work was on x86 memory management and HVM support, but I was also involved in the early stages of the ARM port. Iʼm no longer paid to develop Xen, but I still follow the mailing lists and Iʼm still a maintainer for the x86 shadow pagetable code.

Once upon a time I was a sysadmin, first in the part of UCD computing services that ran the .ie ccTLD, and then in the Secure Hosting division of Baltimore Technologies.

I am not currently looking for work; I have more than enough jobs, thank you.


I have a PhD from the University of Cambridge Computer Laboratory, in the Networks and Operating Systems part of the Systems Research Group. While I was there I was also involved in some infrastructure work for the Xenoservers project. For a while I looked at at processor architectures for network nodes, based on all-optical logic, and specifically at how to do sensible instruction scheduling and data layout on systems with delay-line based memory. My supervisor was Jon Crowcroft. My Erdős number is three.


That goes double for City-of-London jobs. Iʼm not interested in numerical modelling, thanks.
One path from me to Erdős:
Breaking Up is Hard to Do: Security and Functionality in a Commodity Hypervisor, Patrick Colp, Mihir Nanavati, Jun Zhu, William Aiello, George Coker, Tim Deegan, Pete Loscocco and Andrew Warfield. Proc. 23rd ACM SOSP, October 2011.
A random graph model for massive graphs, William Aiello, Fan R. K. Chung, and Linyuan Lu, Proc. 32nd ACM STOC, pp. 171-180, May 2000.
On unavoidable graphs. Fan R. K. Chung, Paul Erdős, Combinatorica 3(2), pp. 167-176, June 1983