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gem5: fix --gem5-readfile
Was completely broken due to confusion between --gem5-readfile and a common variable with the same name which referred to the file path... OMG. Conclusion: no one has ever used this tutorial! Improve ./gem5.sh documentation. Also fix ./gem5-bench-dhrystone.
This commit is contained in:
Ciro Santilli 六四事件 法轮功
87
README.adoc
87
README.adoc
@@ -4541,7 +4541,8 @@ Outcome: <<image-x11>>
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[[image-x11]]
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.X11 Buildroot graphical user interface screenshot
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image::x11.png[image]
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[link=x11.png]
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image::x11.png[]
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We don't build X11 by default because it takes a considerable amount of time (about 20%), and is not expected to be used by most users: you need to pass the `-x` flag to enable it.
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@@ -9941,13 +9942,65 @@ OK, this is why we used gem5 in the first place, performance measurements!
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Let's see how many cycles https://en.wikipedia.org/wiki/Dhrystone[Dhrystone], which Buildroot provides, takes for a few different input parameters.
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First build Dhrystone into the root filesystem:
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We will do that for various input parameters on full system by taking a checkpoint after the boot finishes a fast atomic CPU boot, and then we will restore in a more detailed mode and run the benchmark:
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....
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./build-buildroot --config 'BR2_PACKAGE_DHRYSTONE=y'
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# Boot fast, take checkpoint, and exit.
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./run --arch aarch64 --emulator gem5 --eval-after './gem5.sh'
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# Restore the checkpoint after boot, and benchmark with input 1000.
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./run \
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--arch aarch64 \
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--emulator gem5 \
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--eval-after './gem5.sh' \
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--gem5-readfile 'm5 resetstats;dhrystone 1000;m5 dumpstats' \
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--gem5-restore 1 \
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-- \
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--cpu-type=HPI \
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--restore-with-cpu=HPI \
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--caches \
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--l2cache \
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--l1d_size=64kB \
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--l1i_size=64kB \
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--l2_size=256kB \
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;
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# Get the value for number of cycles.
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# head because there are two lines: our dumpstats and the
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# automatic dumpstats at the end which we don't care about.
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./gem5-stat --arch aarch64 | head -n 1
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# Now for input 10000.
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./run \
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--arch aarch64 \
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--emulator gem5 \
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--eval-after './gem5.sh' \
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--gem5-readfile 'm5 resetstats;dhrystone 10000;m5 dumpstats' \
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--gem5-restore 1 \
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-- \
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--cpu-type=HPI \
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--restore-with-cpu=HPI \
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--caches \
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--l2cache \
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--l1d_size=64kB \
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--l1i_size=64kB \
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--l2_size=256kB \
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;
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./gem5-stat --arch aarch64 | head -n 1
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....
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Then, a flexible setup is demonstrated at:
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If you ever need a shell to quickly inspect the system state after boot, you can just use:
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....
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./run \
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--arch aarch64 \
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--emulator gem5 \
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--eval-after './gem5.sh' \
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--gem5-readfile 'sh' \
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--gem5-restore 1 \
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....
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This procedure is further automated and DRYed up at:
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....
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./gem5-bench-dhrystone
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@@ -9956,28 +10009,26 @@ cat out/gem5-bench-dhrystone.txt
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Source: link:gem5-bench-dhrystone[]
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Sample output:
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Output at 2438410c25e200d9766c8c65773ee7469b599e4a + 1:
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....
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n cycles
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1000 12898577
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10000 23441629
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100000 128428617
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1000 13665219
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10000 20559002
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100000 85977065
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....
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so as expected, the Dhrystone run with a larger input parameter `100000` took more cycles than the ones with smaller input parameters.
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The `gem5-stats` commands output the approximate number of CPU cycles it took Dhrystone to run.
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Another interesting example can be found at: link:gem5-bench-cache[].
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A more naive and simpler to understand approach would be a direct:
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....
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./run --arch aarch64 --emulator gem5 --eval 'm5 checkpoint;m5 resetstats;dhrystone 10000;m5 exit'
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....
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but the problem is that this method does not allow to easily run a different script without running the boot again, see: <<gem5-restore-new-script>>.
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but the problem is that this method does not allow to easily run a different script without running the boot again. The `./gem5.sh` script works around that by using <<m5-readfile>> as explained further at: <<gem5-restore-new-script>>.
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Now you can play a fun little game with your friends:
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@@ -10713,27 +10764,29 @@ So we can do it like:
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....
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# Boot, checkpoint and exit.
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printf 'echo "setup run";m5 exit' > "$(./getvar gem5_readfile)"
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printf 'echo "setup run";m5 exit' > "$(./getvar gem5_readfile_file)"
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./run --emulator gem5 --eval 'm5 checkpoint;m5 readfile > a.sh;sh a.sh'
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# Restore and run the first benchmark.
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printf 'echo "first benchmark";m5 exit' > "$(./getvar gem5_readfile)"
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printf 'echo "first benchmark";m5 exit' > "$(./getvar gem5_readfile_file)"
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./run --emulator gem5 --gem5-restore 1
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# Restore and run the second benchmark.
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printf 'echo "second benchmark";m5 exit' > "$(./getvar gem5_readfile)"
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printf 'echo "second benchmark";m5 exit' > "$(./getvar gem5_readfile_file)"
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./run --emulator gem5 --gem5-restore 1
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# If something weird happened, create an interactive shell to examine the system.
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printf 'sh' > "$(./getvar gem5_readfile)"
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printf 'sh' > "$(./getvar gem5_readfile_file)"
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./run --emulator gem5 --gem5-restore 1
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....
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Since this is such a common setup, we provide some helpers for it as described at <<gem5-run-benchmark>>:
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Since this is such a common setup, we provide the following helpers for this operation:
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* link:rootfs_overlay/lkmc/gem5.sh[]. This script is analogous to gem5's in-tree link:https://github.com/gem5/gem5/blob/2b4b94d0556c2d03172ebff63f7fc502c3c26ff8/configs/boot/hack_back_ckpt.rcS[hack_back_ckpt.rcS], but with less noise.
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* `./run --gem5-readfile` is a convenient way to set the `m5 readfile`
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Their usage us exemplified at <<gem5-run-benchmark>>.
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Other loophole possibilities include:
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* <<9p>>
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@@ -10913,7 +10966,7 @@ https://stackoverflow.com/questions/49516399/how-to-use-m5-readfile-and-m5-execf
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Host:
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....
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date > "$(./getvar gem5_readfile)"
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date > "$(./getvar gem5_readfile_file)"
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....
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Guest:
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@@ -10952,7 +11005,7 @@ Host:
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....
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printf '#!/bin/sh
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echo asdf
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' > "$(./getvar gem5_readfile)"
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' > "$(./getvar gem5_readfile_file)"
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....
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Guest:
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@@ -811,7 +811,7 @@ Incompatible archs are skipped.
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env['stats_file'] = join(env['m5out_dir'], 'stats.txt')
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env['gem5_trace_txt_file'] = join(env['m5out_dir'], 'trace.txt')
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env['gem5_guest_terminal_file'] = join(env['m5out_dir'], 'system.terminal')
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env['gem5_readfile'] = join(env['gem5_run_dir'], 'readfile')
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env['gem5_readfile_file'] = join(env['gem5_run_dir'], 'readfile')
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env['gem5_termout_file'] = join(env['gem5_run_dir'], 'termout.txt')
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env['qemu_run_dir'] = join(env['run_dir_base'], 'qemu', env['arch'], str(env['run_id']))
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env['qemu_termout_file'] = join(env['qemu_run_dir'], 'termout.txt')
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@@ -6,7 +6,7 @@ set -eu
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root_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null && pwd)"
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outfile="${root_dir}/out/gem5-bench-dhrystone.txt"
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arch=aarch64
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cmd="./run --arch '$arch' --emulator gem5 --eval-busybox '/gem5.sh'"
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cmd="./run --arch '$arch' --emulator gem5 --eval-after './gem5.sh'"
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# These cache sizes roughly match the ARM Cortex A75
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# https://en.wikipedia.org/wiki/ARM_Cortex-A75
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@@ -20,7 +20,7 @@ printf 'n cycles\n' > "$outfile"
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for n in 1000 10000 100000; do
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# Restore the most recent checkpoint taken with the more detailed and slower HPI CPU,
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# and run the benchmark with different parameters. We skip the boot completely, saving time!
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eval "${cmd} --gem5-readfile 'dhrystone ${n}' ${restore}" &>/dev/null
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eval "${cmd} --gem5-readfile 'm5 resetstats;dhrystone ${n};m5 dumpstats' ${restore}" &>/dev/null
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printf "${n} " >> "$outfile"
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./gem5-stat -a "$arch" >> "$outfile"
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./gem5-stat --arch "$arch" | head -n 1 >> "$outfile"
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done
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6
run
6
run
@@ -432,8 +432,8 @@ Extra options to append at the end of the emulator command line.
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if not os.path.exists(self.env['linux_image']):
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raise_image_not_found(self.env['image'])
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self.sh.run_cmd([os.path.join(self.env['extract_vmlinux'], self.env['linux_image'])])
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os.makedirs(os.path.dirname(self.env['gem5_readfile']), exist_ok=True)
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self.sh.write_string_to_file(self.env['gem5_readfile'], self.env['gem5_readfile'])
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os.makedirs(os.path.dirname(self.env['gem5_readfile_file']), exist_ok=True)
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self.sh.write_string_to_file(self.env['gem5_readfile_file'], self.env['gem5_readfile'])
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memory = '{}B'.format(self.env['memory'])
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gem5_exe_args = self.sh.shlex_split(self.env['gem5_exe_args'])
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if do_trace:
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@@ -476,7 +476,7 @@ Extra options to append at the end of the emulator command line.
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'--kernel', self.env['image'], LF,
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'--mem-size', memory, LF,
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'--num-cpus', str(self.env['cpus']), LF,
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'--script', self.env['gem5_readfile'], LF,
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'--script', self.env['gem5_readfile_file'], LF,
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])
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if self.env['arch'] == 'x86_64':
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if self.env['kvm']:
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