[alsa-devel] Release of the tool for benchmarking sound server power efficiency

[Alexander E. Patrakov]

Earlier today (sorry - yesterday!) at the audio mini-summit I promised 
to release a tool that I used for evaluating sound server energy 
efficiency. The tool is a shell script, which is attached, together with 
an example report. It needs to be run as root (in a throwaway VM, if you 
need), with one argument: the name of a directory to be created and 
populated with various files. The script needs the "debootstrap" program 
to be installed.

The script will populate the directory with a Debian Jessie amd64 
installation, compile CRAS there, and pack everything into an initramfs 
file that can be used for evaluation. It will produce two files as the 
main result: vmlinuz and initramfs.img, near the directory that it creates.

The initramfs will play a sound file in a loop (please use headphones, 
so that your laptop does not annoy anyone) and log the laptop battery 
energy or charge. If it drops below 75% of the initial value, the 
experiment is terminated, the log is saved to the disk, and the laptop 
is powered off.

You can add this to your boot loader. Example for extlinux:

LABEL battery-pulse7
MENU LABEL Battery Benchmark (pulseaudio 7)
LINUX /boot/battery-benchmark/vmlinuz
INITRD /boot/battery-benchmark/initramfs.img
APPEND quiet root=ram save=/dev/md126p1 test_case=pulse pa_version=7 
latency_msec=28 dobenchmark

Here is the meaning of the arguments:

quiet: don't print verbose messages to the console
root=ram: use ramfs (not tmpfs) for the extracted initramfs
save=/dev/...: save the log to this block device at the end. The 
/battery-reports directory will be created, and the log will be placed 
there. FAT32, NTFS and EXT4 filesystems are supported.
test_case=pulse|alsa|cras: what we want to test. alsa means raw hw device.
pa_version=5|6|7: version of PulseAudio to test
latency_msec: buffer size or its equivalent, in milliseconds
cras_output: the correct output node for CRAS. Usually 5:0 (the default) 
or 6:0, please see cras_test_client --dump_server_info
resampler: force a given resampler for PulseAudio (if not given, no 
resampler is used)
dobenchmark: dpms-blank the screen and perform the measurement automatically

To replicate the results in my presentation, it is sufficient to obtain 
logs for all three versions of PulseAudio, as well as ALSA and CRAS, for 
the following latency_msec values: 7, 28, 448. Please send any reports 
created by this tool to me directly, and mention the laptop model.

A big "thanks" goes to Felipe Sateler for providing Debian packages of 
PulseAudio that are mostly compatible with Debian Jessie.

-- 
Alexander E. Patrakov
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# quiet pcie_aspm=force root=ram save=/dev/md126p1 test_case=pulse pa_version=7 latency_msec=28 dobenchmark initrd=/boot/battery-benchmark/initramfs.img BOOT_IMAGE=/boot/battery-benchmark/vmlinuz 
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