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Ruby's controller block_on behavior aimed to block MessageBuffer requests into SLICC controllers when a Locked_RMW was in flight. Unfortunately, this functionality only partially works: When non-Locked_RMW memory accesses are issued to the sequencer to an address with an in-flight Locked_RMW, the sequencer may pass those accesses through to the controller. At the controller, a number of incorrect activities can occur depending on the protocol. In MOESI_hammer, for example, an intermediate IFETCH will cause an L1D to L2 transfer, which cannot be serviced, because the block_on functionality blocks the trigger queue, resulting in a deadlock. Further, if an intermediate store arrives (e.g. from a separate SMT thread), the sequencer allows the request through to the controller, and the atomicity of the Locked_RMW may be broken. To avoid these problems, disallow the Sequencer from passing any memory accesses to the controller besides Locked_RMW_Write when a Locked_RMW is in- flight.
This is the gem5 simulator. The main website can be found at http://www.gem5.org A good starting point is http://www.gem5.org/Introduction, and for more information about building the simulator and getting started please see http://www.gem5.org/Documentation and http://www.gem5.org/Tutorials. To build gem5, you will need the following software: g++ or clang, Python (gem5 links in the Python interpreter), SCons, SWIG, zlib, m4, and lastly protobuf if you want trace capture and playback support. Please see http://www.gem5.org/Dependencies for more details concerning the minimum versions of the aforementioned tools. Once you have all dependencies resolved, type 'scons build/<ARCH>/gem5.opt' where ARCH is one of ALPHA, ARM, NULL, MIPS, POWER, SPARC, or X86. This will build an optimized version of the gem5 binary (gem5.opt) for the the specified architecture. See http://www.gem5.org/Build_System for more details and options. With the simulator built, have a look at http://www.gem5.org/Running_gem5 for more information on how to use gem5. The basic source release includes these subdirectories: - configs: example simulation configuration scripts - ext: less-common external packages needed to build gem5 - src: source code of the gem5 simulator - system: source for some optional system software for simulated systems - tests: regression tests - util: useful utility programs and files To run full-system simulations, you will need compiled system firmware (console and PALcode for Alpha), kernel binaries and one or more disk images. Please see the gem5 download page for these items at http://www.gem5.org/Download If you have questions, please send mail to gem5-users@gem5.org Enjoy using gem5 and please share your modifications and extensions.