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 used to do PGP, but have given up on it.
If you send me email, please use plain text.
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. It's interesting work, full of distributed and concurrent systems problems and performance optimizations – if thatʼs your idea of fun too, weʼre hiring engineers in Vancouver (Canada) and Cambridge (UK).

Iʼm also one of the maintainers of the Xen hypervisor. I worked full-time on Xen for five and a half years, first at XenSource and then at Citrix after they bought XenSource. These days I mostly review patches and designs on the mailing lists; Iʼm a committer for arch/x86/mm/ and arch/arm/.

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