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Profiling gem5 has indicated computeAddrTop as one of the main contributors in AArch64 simulation time The utility function gets used in the critical path of gem5, which is the memory translation subsystem. The function is supposed to compute a rather trivial task: identifying the "real" most significant bit of a virtual address. This turns out to be quite expensive. Why? The main issue is the AArch32/AArch64 check, which uses the ELIs32 helper. This performs a sequential read of several MiscReg values until it confirms that an EL is indeed using AArch32 (or AArch64). This is functionally accurate but it is too expensive for the critical path of a program. This patch is addressing the issue by adding a Memoizer object for the computeAddrTop function to the CachedState data structure, which is already holding cached system register values for performance reasons. Whenever we need to invalidate those sys reg values because of a change in the translation system, we also flush/invalidate the memoizer cache Change-Id: If42e945c650c293ace304fb4c35e709783bb82d4 Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/59151 Reviewed-by: Jason Lowe-Power <power.jg@gmail.com> Tested-by: kokoro <noreply+kokoro@google.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.