Ari Tamches

email: tamches1@yahoo.com

Current Employment:

Education:

Ph.D. dissertation (2001): Fine-Grained Dynamic Instrumentation of Commodity Operating System Kernels.

My dissertation explores the run-time (dynamic) instrumentation of operating system kernels. Put another way, I explore what can be achieved from a tool that can hot-patch an OS kernel's code on-the-fly. The dissertation details my concrete implementation of such a tool (called kerninstd), as well as some utilities of dynamic kernel instrumentation: OS performance measurement (in another tool, called kperfmon) and dynamic OS optimization via on-the-fly kernel code reorganization (I didn't give this part its own name, so we'll call it kperfmon too). Collectively the tools are known as KernInst, and they are still being developed & maintained by Professor Miller and the Paradyn/KernInst research group at UW-Madison).

You can download my dissertation here (215-or-so pages, PDF format).

Here is a brief run-through of the dissertation.

• Chapter 1 is the introduction. You can read this if you don't want to read the whole thing.
• Chapter 2 discusses related work.
• Chapter 3 describes the KernInst architecture. Some of the grittier low-level algorithms are discussed here, such as CFG and live register analysis of the kernel's code.
• Chapter 4 discusses splicing and code replacement, KernInst's the two central primitives for dynamic kernel instrumentation. As far as low-level details go, this is probably the primary chapter in the dissertation.
• After chapters 3 & 4 have laid down the infrastructure, the second half of the dissertation is able to lighten up somewhat and discuss some real-world uses of the low-level technology. Chapter 5 discusses kernel performance measurement via dynamic instrumentation, and chapter 6 carries on with an OS performance measurement case study.
• Chapter 7 is a fun, if seemingly tangential, diversion. I show that in practice, CFG edge counts can be derived from CFG block counts. This conclusion defies graph theory (which tells you that you can calculate CFG block counts from edge counts, but not vice-versa). The restriction still holds in the general case, but in practice, control flow graphs of code are structured such that it is usually possible to precisely calculate edge execution counts of a function, if given all of its basic block execution counts. 99.6% of CFG edge counts can be determined if given basic block counts, and about 97.8% of functions could determine all of their CFG edge counts given their basic block counts.
• Chapter 8 discusses a real gee-whiz application of dynamic kernel instrumentation. If we can hot-patch the OS kernel code to collect performance information, can't we also hot-patch the OS kernel code to optimize it on the fly? A complete analysis of this subject would take up several dissertations. Here I try to open the door a bit with one specific optimization: improving the I-cache performance of the kernel as it runs.
• Chapter 9 wraps it all up.

Other research papers:

Ariel Tamches and Barton P. Miller. Dynamic Kernel Code Optimization. Workshop on Binary Translation (WBT-2001) , Barcelona, Spain, September 2001. (pdf file, 10 pages)
A 7-page version (pdf) of the above paper was published as part of a TCCA (Technical Committee on Computer Architecture) newsletter in October, 2001.

Ariel Tamches and Barton P. Miller. Fine-Grained Dynamic Instrumentation of Commodity Operating System Kernels. Third Symposium on Operating Systems Design and Implementation (OSDI), February 1999. (Postscript, Compressed, Gzipped, PDF)

Ariel Tamches and Barton P. Miller. Using Dynamic Kernel Instrumentation for Kernel and Application Tuning. International Journal of High Performance Computing Applications, v. 13 no. 3, Fall 1999. (Postscript, Compressed, Gzipped, PDF)

Research Interests:

Click here for the seminal 1994 paper by Hollingsworth, Miller, and Cargille introducing Paradyn's dynamic instrumentation, the inspiration for KernInst. Much of the paper isn't up-to-date with the current version of Paradyn, but it's still fun to read.

KernInst events:

Other Interests: