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Footprint data script details

The footprint_data.sh script runs a number of identical containers sequentially via ctr and takes a number of memory related measurements after each launch. The script is generally not used in a CI type environment, but is intended to be run and analyzed manually.

You can configure the script by setting a number of environment variables.

The following sections list details of the configurable variables, along with a small example invocation script.

Variables

Environment variables can take effect in two ways.

Some variables affect how the payload is executed. The RUNTIME and PAYLOAD arguments directly affect the payload execution with the following line in the script:

$ ctr run --memory-limit $PAYLOAD_RUNTIME_ARGS --rm --runtime=$CONTAINERD_RUNTIME $PAYLOAD $NAME sh -c $PAYLOAD_ARGS

Other settings affect how memory footprint is measured and the test termination conditions.

Variable Function
PAYLOAD The ctr image to run
PAYLOAD_ARGS Any arguments passed into the ctr image
PAYLOAD_RUNTIME_ARGS Any extra arguments passed into the ctr run command
PAYLOAD_SLEEP Seconds to sleep between launch and measurement, to allow settling
MAX_NUM_CONTAINERS The maximum number of containers to run before terminating
MAX_MEMORY_CONSUMED The maximum amount of memory to be consumed before terminating
MIN_MEMORY_FREE The minimum amount of memory allowed to be free before terminating
DUMP_CACHES A flag to note if the system caches should be dumped before capturing stats
DATAFILE Can be set to over-ride the default JSON results filename

Output files

The names of the JSON files generated by the test are dictated by some of the parameters the test is utilising. The default filename is generated in the form of: footprint-${PAYLOAD}[-ksm].json

Measurements

The test measures, calculates, and stores a number of data items:

Item Description
uss USS for all the VM runtime components
pss PSS for all the VM runtime components
all_pss PSS of all of userspace - to monitor if we had other impact on the system
user_smem smem "userspace" consumption value
avail "available" memory from free
avail_decr "available" memory decrease since start of test
cached "Cached" memory from /proc/meminfo
smem_free Free memory as reported by smem
free_decr Decrease in Free memory reported by smem since start of test
anon AnonPages as reported from /proc/meminfo
mapped Mapped pages as reported from /proc/meminfo
cached Cached pages as reported from /proc/meminfo
slab Slab as reported from /proc/meminfo

Example script

The following script is an example of how to configure the environment variables and invoke the test script to run a number of different container tests.

#!/bin/bash

set -e
set -x

export MAX_NUM_CONTAINERS=10
export MAX_MEMORY_CONSUMED=6*1024*1024*1024

function run() {
	###
	# Define what we will be running (app under test)
	#  Default is we run busybox, as a 'small' workload
	export PAYLOAD="quay.io/prometheus/busybox:latest"
	export PAYLOAD_ARGS="tail -f /dev/null"
	export PAYLOAD_SLEEP=10
	export PAYLOAD_RUNTIME_ARGS="5120"
	sudo -E bash $(pwd)/density/footprint_data.sh
}

export CONTAINERD_RUNTIME=io.containerd.kata.v2
run