gem5: namespace checkpoints by arch

Also refactor common gem5 x86 and arm command parts

README.adoc

@@ -1791,7 +1791,7 @@ These commands output the approximate number of CPU cycles it took Dhrystone to
 
 It works like this:
 
-* the first commond boots linux with the default simplified `AtomicSimpleCPU`, and generates a <<gem5-checkpoint,checkpoint>> after the kernel boots and before running the benchmark
+* the first command boots linux with the default simplified `AtomicSimpleCPU`, and generates a <<gem5-checkpoint,checkpoint>> after the kernel boots and before running the benchmark
 * the second command restores the checkpoint with the more detailed `HPI` CPU model, and runs the benchmark. We don't boot with it because that is much slower.
 
 ARM employees have just been modifying benchmarking code with instrumentation directly: https://github.com/arm-university/arm-gem5-rsk/blob/aa3b51b175a0f3b6e75c9c856092ae0c8f2a7cdc/parsec_patches/xcompile-patch.diff#L230
@@ -2267,10 +2267,10 @@ Analogous to QEMU's <<snapshot>>, but better since it can be started from inside
 Documentation: http://gem5.org/Checkpoints
 
 ....
-./rung -a arm -g
+./run -a arm -g
 ....
 
-In guest, wait for the boot to end and run:
+In the guest, wait for the boot to end and run:
 
 ....
 m5 checkpoint
@@ -2279,7 +2279,7 @@ m5 checkpoint
 To restore the checkpoint, kill the VM and run:
 
 ....
-./rung -a arm -g -- -r 1
+./run -a arm -g -- -r 1
 ....
 
 Let's create a second checkpoint to see how it works, in guest:
@@ -2303,11 +2303,6 @@ cat f
 
 contains the `date`. The file `f` wouldn't exist had we used the first checkpoint with `-r 1`.
 
-Internals:
-
-* the checkpoints are stored under `m5out/cpt.*`
-* `m5` is a guest utility present inside the gem5 tree which we cross-compiled and installed into the guest
-
 If you automate things with <<kernel-command-line-parameters>> as in:
 
 ....
@@ -2322,6 +2317,20 @@ Then there is no need to pass the kernel command line again to gem5 for replay:
 
 since boot has already happened, and the parameters are already in the RAM of the snapshot.
 
+Our scripts "namespace" with the checkpoint by architecture with `--checkpoint-dir`, so if you make two checkpoints:
+
+* one in x86
+* the other in arm
+
+Then you would still restore both of them with `-- -r 1`.
+
+This makes it easier to remember which checkpoint is which, especially since there appears to be no runtime way to set the checkpoint names.
+
+Internals:
+
+* the checkpoints are stored under `m5out/cpts/$arch/cpt.$todo_whatisthis`
+* `m5` is a guest utility present inside the gem5 tree which we cross-compiled and installed into the guest
+
 ==== gem5 restore checkpoint with a different CPU
 
 gem5 can switch to a different CPU model when restoring a checkpoint.

run

@@ -74,35 +74,37 @@ out_dir="${root_dir}/buildroot/output.${arch_dir}~"
 if "$gem5"; then
   build_dir="${out_dir}/build/gem5-1.0"
   gem5_dir="${build_dir}/gem5"
+  if [ "$arch" = x86_64 ]; then
+    gem5_arch=X86
+  else
+    gem5_arch=ARM
+  fi
+  gem5_cpt_dir="./m5out/cpts/${arch}"
+  mkdir -p "$gem5_cpt_dir"
+  gem5_common="\
+M5_PATH='${build_dir}/system' \
+$debug_vm \
+'${gem5_dir}/build/${gem5_arch}/gem5.opt' \
+${gem5opts} \
+'${gem5_dir}/configs/example/fs.py' \
+--checkpoint-dir='${gem5_cpt_dir}' \
+--disk-image='${out_dir}/images/rootfs.ext2' \
+--kernel='${out_dir}/build/linux-custom/vmlinux' \
+--num-cpus='${cpus}' \
+"
   if [ "$arch" = x86_64 ]; then
     if "$kvm"; then
       extra_flags="$extra_flags --cpu-type=X86KvmCPU"
     fi
-    cmd="\
-M5_PATH='${build_dir}/system' \
-$debug_vm \
-'${gem5_dir}/build/X86/gem5.opt' \
-${gem5opts} \
-'${gem5_dir}/configs/example/fs.py' \
+    cmd="${gem5_common} \
 --command-line='earlyprintk=ttyS0 console=ttyS0 lpj=7999923 root=/dev/hda $extra_append' \
---disk-image='${out_dir}/images/rootfs.ext2' \
---kernel='${out_dir}/build/linux-custom/vmlinux' \
---num-cpus=${cpus} \
 $extra_flags \
 "
   elif [ "$arch" = arm ] || [ "$arch" = aarch64 ]; then
-    cmd="\
-M5_PATH='${build_dir}/system' \
-$debug_vm \
-'${gem5_dir}/build/ARM/gem5.opt' \
-${gem5opts} \
-'${gem5_dir}/configs/example/fs.py' \
+    cmd="${gem5_common} \
 --command-line='earlyprintk=pl011,0x1c090000 console=ttyAMA0 lpj=19988480 rw loglevel=8 mem=512MB root=/dev/sda $extra_append' \
---disk-image='${out_dir}/images/rootfs.ext2' \
 --dtb-file='${gem5_dir}/system/arm/dt/$([ "$arch" = arm ] && echo "armv7_gem5_v1_${cpus}cpu" || echo "armv8_gem5_v1_${cpus}cpu").dtb' \
---kernel='${out_dir}/build/linux-custom/vmlinux' \
 --machine-type=VExpress_GEM5_V1 \
---num-cpus='${cpus}' \
 $extra_flags \
 "
   fi