Thread-Level Speculation with Kernel Support

This repository contains the source code of the K-TLS and U-TLS systems as described in this paper (also available on ACM; download paper as PDF or slides):

C. Hammacher, K. Streit, A. Zeller and S. Hack. Thread-Level Speculation with Kernel Support. In Proceedings of the 25th International Conference on Compiler Construction (CC '16), pages 1-11, March 2016.

Additionally, the sources of the improved tinySTM implementation (with improved data structures for better scalability) is included.

Building

The software (TinySTM, U-TLS and K-TLS) is split into different directories in the lib folder. All this software can be built by running the make command. If you need to pass additional compiler or preprocessor flags, you place them in the corresponding environment variables, for example like this:

  CPPFLAGS=-I/usr/local/include make

The kernel module is compiled for the currently running kernel. If the directory /lib/modules/$(uname -r)/build does not exist, the Makefile will output a warning and skip compilation of the kernel module.

Usage

Before running experiments using K-TLS, make sure to load the kernel module. Since this is very experimental, I strongly recommend to run this in a virtual machine only!

  sudo insmod lib/KTLS/kmod/KTLS.ko

For debugging, load the module with the debug level set to 3 or 4, and observe the kernel messages printed:

  sudo insmod lib/KTLS/kmod/KTLS.ko debug=3
  dmesg -wT

The API (for both C and C++) for creating a task list is documented in the tls.h header file. This task list can then be run either in K-TLS or in U-TLS by running the ktls_run (see ktls.h header file) or utls_run (see utls.h header file) function respectively.

For K-TLS, there is also a loop interface, which makes instrumentation easier for speculative loop parallelization. Currently, the implementation just internally aggregates a task for each iteration, and spawns them once 16 tasks are available.

A few example usages of the interface are available in the test directory.

Authors

This software was written by Clemens Hammacher, with contributions by Daniel Birtel and Janosch Gräf.

License

Both U-TLS and K-TLS are available under the GNU General Public License v3.