Hi,
On Fri, Nov 18, 2016 at 12:36 PM, H. Nikolaus Schaller hns@goldelico.com wrote:
What does "high-load" mean exactly?
Driving both cores to 100% load by running bash in loops:
http://git.goldelico.com/?p=gta04-kernel.git;a=blob;f=Letux/root/high-load;h...
Well, this might not be an optimal test since in theory every piece could fit in I/D-caches, but it is unlikely.
From our experience of overclocking pandora we know that "simple"
loops like that don't really stress the CPU much, overclocked pandora will crash a lot sooner if NEON is used (and it will use more power). Try the attached program instead, it heats the CPU to 100C much quicker, meanwhile a bash loop takes a lot of time to do the same:
50C->100C on my uEVM (heatsink attached, room temperature 20C or so) bash: does not reach 100C (only does if the board is covered by antistatic bag) neon: ~11min
Compile with: gcc -o neon_loop neon_loop.S -mfpu=neon -mcpu=native The program is probably far from a maximum stresser, but it at least tries to load all the CPU pipelines with work, including NEON.
That also brings to another observation: the current kernel is doing thermal throttling. If you watch current CPU frequency while the temperature is ~100C, you'll see the frequency sometimes dropping to 1GHz even with both cores at 100% and performance governor active. And indeed, /sys/class/thermal/thermal_zone0/trip_point_0_temp specifies 100000, which must be the point it starts to throttle.
Now, for my uEVM tests: - my usual 12V supply: still rock stable on 4.9.0-rc5-letux+ (>1h test)
I've found a supply ED sent me long ago for GP2X (it needs some unusual voltage) which has a voltage switch: - 4.5V setting, multimeter shows ~4.8V at the board connector on load - hung after ~20min or so - 5V setting, ~5.3V actually measured on load - survived for 14h (2x neon_loop + memtester, also tried bash loop + memtester for a few hours)
Gražvydas