Version 21.0 marks one full year of gem5 releases, and on this anniversary, I think we have some of the biggest new features yet! This has been a very productive release with 100 issues, over 813 commits, and 49 unique contributors.
This new protocol provides a single cache controller that can be reused at multiple levels of the cache hierarchy and configured to model multiple instances of MESI and MOESI cache coherency protocols. This implementation is based of Arm’s AMBA 5 CHI specification and provides a scalable framework for the design space exploration of large SoC designs.
See the gem5 documentation for more details. There is also a gem5 blog post on this new protocol as well.
In previous releases, this model was only partially supported. As of gem5 21.0, this model has been fully integrated and is tested nightly. This model currently only works in syscall emulation mode and requires using the gcn docker container to get the correct version of the ROCm stack. More information can be found in this blog post.
With this full support, we are also providing many applications as well. See gem5-resources for more information.
The RISC-V model in gem5 can now boot unmodified Linux! Additionally, we have implemented DTB generation and support the Berkeley Boot Loader as the stage 1 boot loader. We have also released a set of resources for you to get started: https://gem5.googlesource.com/public/gem5-resources/+/refs/heads/develop/src/riscv-fs/
There are multiple places where the developers have reduced boilerplate.
create() functions! Previously, every SimObject required a <SimObjectParams>::create() function to be manually defined. Forgetting to do this resulted in confusing errors. Now, this function is created for you automatically. You can still override it if you need to handle any special cases.params(): Rather than defining a typedef and the params() function for every SimObject, you can now use the PARAMS macro.See http://doxygen.gem5.org/release/current/classSimObject.html#details for more details on these two API changes.
Group) is still supported, but it is now deprecated.Group API, it may not be automatically dumped using new stat APIs (e.g., the Python API).StaticInst type