Bandwatch

Eric Seals ([email protected])

Preparation

Recommended kernel settings are as follows:

CONFIG_ACPI_PROCESSOR=n
CONFIG_CPU_IDLE=n

Build and Install

On a Jetson product in the bandwatch directory, first compile the code:

$ make

Load the kernel mode and specify Tegra X1 hardware memory counter:

$ insmod memguard.ko g_hw_counter_id=0x17

Usage

Once the module is loaded, Bandwatch can be used for dynamic memory regulation in an effort to maintain RT CPU core performance against co-running CPU and GPU applications. The current configuration will protect CPU core 0 against interference.

A note on memory controller utilization on Tegra. The MC runs at a clock speed of 1.6GHz so at a 10us sample period, 10% utilization is measured as 1600 ticks by the activity monitor.

Figures

Figures used in the paper can be produced the shell scripts available in the /tests/plots directory.

Individual Components

The Memory Activity Monitor and GPU throttling mechanism can be tested individually by exploring the individual_modules directory.

GPU Throttle

On a Jetson product in the /bandwatch/individual_modules/throttle directory:

$ make
$ insmod throttle.ko

The throttling level is controlled using the debugfs interface. On Tegra X1 architectures, the memory throttling has the granularity of 32 levels. For example, the following sets the level to 8:

$ echo 8 > /sys/kernel/debug/throttle/throttle

Activity Monitor

On a Jetson product in the /bandwatch/individual_modules/actmon directory:

$ make
$ insmod actmon.ko

You can run the simple script logACTMON.sh to output to the console, every 100ms, the total average count of memory cycles within the memory controller.