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Why performance is higher on LITTLE cores?

zois

Hi all,

I am using the HiKey970 board to run inferences on neural networks. The board comprises ARM Cortex-A73 and ARM Cortex-A53 cores.
I am using `taskset` to pin the inference process (that spawns 4 threads) once on the LITTLE cores (0-3) and once on the big cores (4-7). Contrary to what I was expecting, the inference time is almost double when running on big cores, compared to LITTLE cores.

Is there an explanation for this behavior? Are there tools that can help me understand why the threads are slower when using big cores?

To be more precise, the board is flashed with kernel version 4.9.78-147538-g244928755bbe, the code that I am using can be found in this repo.

Parents
  • 0 in reply to Willy Wolff

    Thanks for the advice, I will try it out.

    Posting the following, regarding setting the memory and GPU frequency, in case someone else comes across this thread.
    For the specific distribution, kernel and device (Lebian, 4.9.78-147538-g244928755bbe, HikEy 970),

    /sys/devices/platform/ddr_devfreq/devfreq/ddr_devfreq/cur_freq

    does not have writing privileges. Even if we modify the privileges and write the file, the frequency does not seem to change. Instead, if we change the memory or GPU governor to `userspace`, there is a new directory, named `userspace,` created under

    /sys/devices/platform/ddr_devfreq/devfreq/ddr_devfreq
    .
    Within that directory, there is a file `cur_freq` that we can write and set the frequency in the desired value.

Reply
  • 0 in reply to Willy Wolff

    Thanks for the advice, I will try it out.

    Posting the following, regarding setting the memory and GPU frequency, in case someone else comes across this thread.
    For the specific distribution, kernel and device (Lebian, 4.9.78-147538-g244928755bbe, HikEy 970),

    /sys/devices/platform/ddr_devfreq/devfreq/ddr_devfreq/cur_freq

    does not have writing privileges. Even if we modify the privileges and write the file, the frequency does not seem to change. Instead, if we change the memory or GPU governor to `userspace`, there is a new directory, named `userspace,` created under

    /sys/devices/platform/ddr_devfreq/devfreq/ddr_devfreq
    .
    Within that directory, there is a file `cur_freq` that we can write and set the frequency in the desired value.

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