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gem5: take one quick failed shot at se.py --smt

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Ciro Santilli 六四事件 法轮功
2020-04-25 01:00:00 +00:00
parent d0aac8d6f9
commit 7f332f2412
1 changed files with 25 additions and 2 deletions
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README.adoc
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@@ -4150,7 +4150,7 @@ and then <<dry-run,hack the produced command>> by replacing:
with:
....
--cmd '/home/ciro/bak/git/linux-kernel-module-cheat/out/userland/default/aarch64/posix/getpid.out;/home/ciro/bak/git/linux-kernel-module-cheat/out/userland/default/aarch64/posix/getpid.out' \
--cmd '/path/to/linux-kernel-module-cheat/out/userland/default/aarch64/posix/getpid.out;/path/to/linux-kernel-module-cheat/out/userland/default/aarch64/posix/getpid.out' \
--param 'system.cpu[:].workload[:].release = "5.4.3"' \
....
@@ -4190,6 +4190,29 @@ which starts with:
and therefore shows one instruction running on each CPU for each process at the same time.
===== gem5 syscall emulation --smt
gem5 b1623cb2087873f64197e503ab8894b5e4d4c7b4 syscall emulation has an `--smt` option presumably for <<hardware-threads>> but it has been neglected forever it seems: https://github.com/cirosantilli/linux-kernel-module-cheat/issues/104
If we start from the manually hacked working command from <<gem5-syscall-emulation-multiple-executables>> and try to add:
....
--cpu 1 --cpu-type Derivo3CPU --caches
....
We choose <<gem5-deriveo3cpu,`DerivO3CPU`>> because of the se.py assert:
....
example/se.py:115: assert(options.cpu_type == "DerivO3CPU")
....
But then that fails with:
....
gem5.opt: /path/to/linux-kernel-module-cheat/out/gem5/master3/build/ARM/cpu/o3/cpu.cc:205: FullO3CPU<Impl>::FullO3CPU(DerivO3CPUParams*) [with Impl = O3CPUImpl]: Assertion `params->numPhysVecPredRegs >= numThreads * TheISA::NumVecPredRegs' failed.
Program aborted at tick 0
....
=== QEMU user mode quirks
==== QEMU user mode does not show stdout immediately
@@ -22499,7 +22522,7 @@ Intel name: "Hyperthreading"
* https://stackoverflow.com/questions/5593328/software-threads-vs-hardware-threads/61415402#61415402
* https://superuser.com/questions/122536/what-is-hyper-threading-and-how-does-it-work
gem5 appears to possibly have attempted to implement hardware threads in <<gem5-syscall-emulation-mode>>: https://github.com/cirosantilli/linux-kernel-module-cheat/issues/104 when using <<gem5-syscall-emulation-multiple-executables>>.
gem5 appears to possibly have attempted to implement hardware threads in <<gem5-syscall-emulation-mode>> as mentioned at <<gem5-syscall-emulation-smt>>.
On fs.py it is not exposed in any in-tree config however, and as pointed by the above issue O3 FS has an assert that prevents it in https://github.com/gem5/gem5/blob/377898c4034c72b84b2662ed252fa25079a4ea62/src/cpu/o3/cpu.cc#L313[src/cpu/o3/cpu.cc]: