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T2 building small arm binaries

December 06, 2016 — BarryK
I posted yesterday about compiling 'xdelta3' statically in buildroot, native build on my Pi3:

The 'xdelta3' binary is very small.

Now T2 is running on my Pi3, building the same selection of packages as used in Quirky April x86, as described here:

The build is taking days. Quite literally, days. Right now, it is compiling some media libraries. I don't have a UPS, so hope the mains power supply doesn't hiccup.

I have just been comparing the sizes of executables compiled by T2 with those in my running Quirky host, which is based upon Ubuntu armhf DEBs. The T2 binaries are smaller, no always, but in majority of cases.

In the T2 configuration, I chose the "cortex-a8" ARM CPU, and enabled thumb instructions.
When compiling, T2 uses these options for gcc:

-mcpu=cortex-a8 -mthumb -mthumb-interwork

I thought maybe the thumb instructions is the reason for the smaller binaries, however, I googled and found that Ubuntu and Debian armhf DEBs also are built with thumb-2 support.

So, I don't know why T2 is building smaller binaries.

Anyway, I am having to "cool my heels". Want to compile in buildroot, but can't until T2 has finished. Some other work also has to wait.


T2 has been running for a couple of days, with pauses. Stopped earlier, running again this afternoon, has been going for about 4 hours.

T2 is set to run with 3 cores. I reported some temperatures earlier:

Outside temperature is 23 degrees C. 6pm, so later afternoon. Don't know what it is inside, probably about that.

The CPU governor is set to "performance", and this is the temp:

# /opt/vc/bin/vcgencmd measure_temp

Worries me, that, a bit too high for my liking.

After T2 is finished, I reckon will stick another heatsink underneath the board, on the RAM chip.
My Pi3 is in a case, with heatsinks on top, and the lid left off. But circulation underneath is not good. Might cut a hole on the underneath and stick on a finned heatsink -- that will be unusual!

Why not? The Pi could stand on it's side, with fins sticking out both sides.

Tags: linux