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Gem5 Hardware Transactional Memory (HTM) Here we provide a brief note describing HTM support in Gem5 at a high level. HTM is an architectural feature that enables speculative concurrency in a shared-memory system; groups of instructions known as transactions are executed as an atomic unit. The system allows that transactions be executed concurrently but intervenes if a transaction's atomicity/isolation is jeapordised and takes corrective action. In this implementation, corrective active explicitely means rolling back a thread's architectural state and reverting any memory updates to a point just before the transaction began. This HTM implementation relies on-- (1) A checkpointing mechanism for architectural register state. (2) Buffering speculative memory updates. This patch is focusing on the definition of the HTM checkpoint (1) The checkpointing mechanism is architecture dependent. Each ISA leveraging HTM support can define a class HTMCheckpoint inhereting from the generic one (GenericISA::HTMCheckpoint). Those will need to save/restore the architectural state by overriding the virtual HTMCheckpoint::save (when starting a transaction) and HTMCheckpoint::restore (when aborting a transaction). Instances of this class live in O3's ThreadState and Atomic's SimpleThread. It is up to the ISA to populate this instance when executing an instruction that begins a new transaction. JIRA: https://gem5.atlassian.net/browse/GEM5-587 Change-Id: Icd8d1913d23652d78fe89e930ab1e302eb52363d Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/30314 Reviewed-by: Jason Lowe-Power <power.jg@gmail.com> Maintainer: 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, SWIG, 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 the aforementioned tools. Once you have all dependencies resolved, type 'scons build/<ARCH>/gem5.opt' where ARCH is one of 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/documentation/general_docs/building for more details and options. 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. If you have questions, please send mail to gem5-users@gem5.org Enjoy using gem5 and please share your modifications and extensions.