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This patch adds a stand-alone stack distance calculator. The stack distance calculator is a passive SimObject that observes the addresses passed to it. It calculates stack distances (LRU Distances) of incoming addresses based on the partial sum hierarchy tree algorithm described by Alamasi et al. http://doi.acm.org/10.1145/773039.773043. For each transaction a hashtable look-up is performed. At every non-unique transaction the tree is traversed from the leaf at the returned index to the root, the old node is deleted from the tree, and the sums (to the right) are collected and decremented. The collected sum represets the stack distance of the found node. At every unique transaction the stack distance is returned as numeric_limits<uint64>::max(). In addition to the basic stack distance calculation, a feature to mark an old node in the tree is added. This is useful if it is required to see the reuse pattern. For example, Writebacks to the lower level (e.g. membus from L2), can be marked instead of being removed from the stack (isMarked flag of Node set to True). And then later if this same address is accessed (by L1), the value of the isMarked flag would be True. This gives some insight on how the Writeback policy of the lower level affect the read/write accesses in an application. Debugging is enabled by setting the verify flag to true. Debugging is implemented using a dummy stack that behaves in a naive way, using STL vectors. Note that this has a large impact on run time.
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.