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When GPU needs more scratch it requests from the runtime. In the method to wait for response, a dmaReadVirt is called with the same method as the callback with zero delay. This means that effectively there is an infinite loop in the event queue if the scratch setup is not successful on the first attempt. In the case of GPUFS, it is never successfully instantly so a delay must be added. Without added delay, the host CPU is never scheduled to make progress setting up more scratch space. The value 1e9 is choosen to match the KVM quantum and hopefully give KVM a chance to schedule an event. For reference, the driver timeout is 200ms so this is still fairly aggressive checking of the signal response. This value is also balanced around the GPUCommandProc DPRINTF to prevent the print in this method from overwhelming debug output. Change-Id: I0e0e1d75cd66f7c47815b13a4bfc3c0188e16220 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/61651 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Matt Sinclair <mattdsinclair@gmail.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.