Power Saving modes on BBB?

Oliver Grawert ogra at ubuntu.com
Thu Jul 30 12:23:28 UTC 2015

Am Donnerstag, den 30.07.2015, 12:52 +0200 schrieb Gábor Paller:

> Linux localhost.localdomain 3.19.0-18-generic #18-Ubuntu SMP Tue May 
ah, that might be the issue ;)
(BeagleBoneBlack)ubuntu at localhost:~$ uname -a
Linux localhost.localdomain 3.19.0-23-generic #24-Ubuntu SMP Tue Jul 7
18:56:34 UTC 2015 armv7l armv7l armv7l GNU/Linux

> This is a 15.04 Snappy on BBB without any kernel hacking.
> "is this under the same userspace too (i.e. are you sure it is kernel
> induced and not some bad userspace component) ?"
> My test is the following. I created an SD card from the stock Snappy
> image, flashed it and booted it. I waited for the boot sequence to
> finish and waited for the idle prompt. I measure 340 mA of
> consumption. I did the same with the TI SDK and I measure 250 mA.
> Hence the 40% difference.
> As with any Linux distribution it is not only the "kernel" that is
> running in any of these cases but a bunch of drivers/daemons too. But
> there is no userspace component in these cases, at least I did not
> install/run any.
well, i'm just trying to find out if "TI SDK" means you have your own
rootfs or if you just put vmlinuz and the modules from the TI SDK into
an already installed snappy system ... 

there can be plenty differences on kernel level (does the TI kernel
actually have all needed apparmor patches for example). but i would
expect userspace difference too if you dont use the very same rootfs for
measuring both.

to identify if the higher power consumption is a kernel or userspace
thing you can indeed only measure reliably by using the same environment
to run the different kernels in, else you might for example have
userspace bits that turn different knobs in sysfs on boot etc which will
definitely get you different hardware behavior.


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