Apparently the original upstream docs PR was wrong about vm_memory_high_watermark's absolute units -- they're bytes unless specified as a string with a suffix

Author: tianon

docker-entrypoint.sh

@@ -221,12 +221,12 @@ if [ "$1" = 'rabbitmq-server' ] && [ "$shouldWriteConfig" ]; then
 		"{ loopback_users, $(rabbit_array) }"
 	)
 
-	# https://github.com/rabbitmq/rabbitmq-website/pull/96/files
+	# https://www.rabbitmq.com/memory.html#memsup-usage
 	# "If the absolute limit is larger than the installed RAM or available virtual address space, the threshold is set to whichever limit is smaller."
 	# specifically, if a memory limit isn't supplied to the container and "memory.limit_in_bytes" is thus an enormous constant, RabbitMQ will ignore it and use maximum available memory or address space instead
 	if [ -r /sys/fs/cgroup/memory/memory.limit_in_bytes ]; then
 		memLimit="$(< /sys/fs/cgroup/memory/memory.limit_in_bytes)"
-		rabbitConfig+=( "{ vm_memory_high_watermark, { absolute, $(( memLimit / 1024 / 1024 )) } }" )
+		rabbitConfig+=( "{ vm_memory_high_watermark, { absolute, $memLimit } }" )
 	fi
 
 	if [ "$haveSslConfig" ]; then