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The current MESI_Two_Level protocol's L1 caches updates the MRU information twice per request on misses -- once when the request reaches Ruby and once when the miss is returned from another level of the memory hierarchy. Although this approach does not cause any correctness bugs for replacement policies like LRU since this request is the LRU in both cases, it does not work correctly for other policies like SecondChance and LFU, where updating the information twice (for misses) causes them to devolve to LRU. Note that this was not directly a problem with Ruby previously, because it only supported LRU-based policies that were unaffected by this. However, with the integration of 20879 Ruby now uses the same replacement policies as Classic (which has additional, non-LRU based replacement policies). This patch resolves this problem by not updating the MRU information a second time for the misses. It has been tested and validated with the replacement policy tests. Change-Id: I9e7e96a9d6c09f3d6b7daae7115ef091ac3bdc08 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/64371 Reviewed-by: Jason Lowe-Power <power.jg@gmail.com> Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com> Tested-by: kokoro <noreply+kokoro@google.com> Maintainer: Matt Sinclair <mattdsinclair@gmail.com>
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/about, and for more information about building the simulator and getting started please see http://www.gem5.org/documentation and http://www.gem5.org/documentation/learning_gem5/introduction. To build gem5, you will need the following software: g++ or clang, Python (gem5 links in the Python interpreter), SCons, zlib, m4, and lastly protobuf if you want trace capture and playback support. Please see http://www.gem5.org/documentation/general_docs/building for more details concerning the minimum versions of these tools. Once you have all dependencies resolved, type 'scons build/<CONFIG>/gem5.opt' where CONFIG is one of the options in build_opts like ARM, NULL, MIPS, POWER, SPARC, X86, Garnet_standalone, etc. This will build an optimized version of the gem5 binary (gem5.opt) with the the specified configuration. See http://www.gem5.org/documentation/general_docs/building for more details and options. The main source tree includes these subdirectories: - build_opts: pre-made default configurations for gem5 - build_tools: tools used internally by gem5's build process. - configs: example simulation configuration scripts - ext: less-common external packages needed to build gem5 - include: include files for use in other programs - site_scons: modular components of the build system - 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 may need compiled system firmware, kernel binaries and one or more disk images, depending on gem5's configuration and what type of workload you're trying to run. Many of those resources can be downloaded from http://resources.gem5.org, and/or from the git repository here: https://gem5.googlesource.com/public/gem5-resources/ If you have questions, please send mail to gem5-users@gem5.org Enjoy using gem5 and please share your modifications and extensions.