dm-cache/cachestats.sh

#!/bin/bash

# cachestats for dm-cache
#
# SPDX-License-Identifier: GPL-3.0-or-later
# Copyright 2023 Forza <forza@tnonline.net>

device_name="$1"

# Declare an associative array to store key-value pairs
declare -A data
declare -i sizess
declare status_output
declare -a dmstatus

# Get the status output using dmsetup
status_output=$(dmsetup status "$device_name" 2>/dev/null)

# Check if the device exists and has valid output
if [ -n "$status_output" ]; then
	sizess=$(blockdev --getss "/dev/mapper/${device_name}")
	
	# Parse the status information into the associative array
	IFS='/: ' read -r -a dmstatus <<< "$status_output"
	
	## Ouput `dmsetup status` raw data:
	#	for ((i = 0; i < ${#dmstatus[@]}; i += 1)); do
	#		echo \# $i: ${dmstatus["$i"]}
	#	done
	
	# Field order of `dmsetup status <cachedev>`:
	# https://www.kernel.org/doc/html/latest/admin-guide/device-mapper/cache.html
	#
	# <metadata block size> <#used metadata blocks>/<#total metadata blocks>
	# <cache block size> <#used cache blocks>/<#total cache blocks>
	# <#read hits> <#read misses> <#write hits> <#write misses>
	# <#demotions> <#promotions> <#dirty> <#features> <features>*
	# <#core args> <core args>* <policy name> <#policy args> <policy args>*
	# <cache metadata mode>

	data["name"]="$device_name"
	data["origin_start"]=$(( ${dmstatus[0]} * $sizess )) # in sectors
	data["origin_length"]=$(( ${dmstatus[1]} * $sizess )) # in sectors
	data["table_type"]="${dmstatus[2]}"
	data["metadata_block_size"]=$(( ${dmstatus[3]} * $sizess )) # in sectors
	data["used_metadata_blocks"]="${dmstatus[4]}"
	data["total_metadata_blocks"]="${dmstatus[5]}"
	data["cache_block_size"]=$(( ${dmstatus[6]} * $sizess )) # in sectors
	data["used_cache_blocks"]="${dmstatus[7]}"
	data["total_cache_blocks"]="${dmstatus[8]}"
	data["read_hits"]="${dmstatus[9]}"
	data["read_misses"]="${dmstatus[10]}"
	data["write_hits"]="${dmstatus[11]}"
	data["write_misses"]="${dmstatus[12]}"
	data["demotions"]="${dmstatus[13]}"
	data["promotions"]="${dmstatus[14]}"
	data["dirty_cache"]=$(( ${dmstatus[15]} * ${data[cache_block_size]} ))
	if [ "${dmstatus[16]}" = 2 ]; then
		data["cache_type"]="${dmstatus[17]}"
		data["discard_passdown"]="${dmstatus[18]}"
		data["migration_threshold"]=$(( ${dmstatus[21]} * $sizess ))
		data["cache_policy"]="${dmstatus[22]}"
		data["smq_count"]="${dmstatus[23]}"
		data["cache_rw"]="${dmstatus[24]}"
		data["status"]="${dmstatus[25]//-/OK}"
	else
		data["cache_type"]="${dmstatus[17]}"
		data["discard_passdown"]="true"
		data["migration_threshold"]=$(( ${dmstatus[20]} * $sizess ))
		data["cache_policy"]="${dmstatus[21]}"
		data["smq_count"]="${dmstatus[22]}"
		data["cache_rw"]="${dmstatus[23]}"
		data["status"]="${dmstatus[24]//-/OK}"
	fi

# Loop through throuh all fields to list and print their values
#	for field in "${!data[@]}"; do
#		value="${data[$field]}"
#		if [ -n "$value" ]; then
#			echo "$field : $value"
#		else
#			echo "Field '$field' not found."
#		fi
#	done |sort

	# Output defined fields
	printf "\n"
	printf "DEVICE\n"
	printf "========\n"
	printf "%-*s%s\n" "30" "Device-mapper device: " "${data[name]}"
	printf "%-*s%s\n" "30" "Origin size: " "$(( ${data[origin_length]} - ${data[origin_start]} )) bytes"
	printf "%-*s%s\n" "30" "Discards: " "${data[discard_passdown]}"

	printf "\n"
	printf "CACHE\n"
	printf "========\n"
	printf "%-*s%s\n" "30" "Cache Size: " "$(( ${data[total_cache_blocks]} * ${data[cache_block_size]} )) bytes"
	printf "%-*s%s\n" "30" "Cache Usage: "  "$(( ${data[used_cache_blocks]} * ${data[cache_block_size]} )) bytes"
	printf "%-*s%s\n" "30" "Cache Usage: " "$(( 100 * ${data[used_cache_blocks]} / ${data[total_cache_blocks]} )) %"
	printf "%-*s%s\n" "30" "Cache Read Hit: " "${data[read_hits]}"
	printf "%-*s%s\n" "30" "Cache Read Miss: " "${data[read_misses]}"
	printf "%-*s%s\n" "30" "Cache Write Hit: " "${data[write_hits]}"
	printf "%-*s%s\n" "30" "Cache Write Miss: " "${data[write_misses]}"
	printf "%-*s%s\n" "30" "Cache Dirty: " "${data[dirty_cache]} bytes"
	printf "%-*s%s\n" "30" "Cache Block Size: " "${data[cache_block_size]} bytes"
	printf "%-*s%s\n" "30" "Cache Promotions: " "${data[promotions]}"
	printf "%-*s%s\n" "30" "Cache Demotions: " "${data[demotions]}"
	printf "%-*s%s\n" "30" "Cache Migration Threshold: " "${data[migration_threshold]} bytes"
	printf "%-*s%s\n" "30" "Cache RW mode: " "${data[cache_rw]}"
	printf "%-*s%s\n" "30" "Cache Type: " "${data[cache_type]}"
	printf "%-*s%s\n" "30" "Cache Policy: " "${data[cache_policy]}"
	printf "%-*s%s\n" "30" "Cache Status: " "${data[status]}"

	printf "\n"
	printf "METADATA\n"
	printf "========\n"
	printf "%-*s%s\n" "30" "Metadata Size: " "$(( ${data[total_metadata_blocks]} * ${data[metadata_block_size]} )) bytes"
	printf "%-*s%s\n" "30" "Metadata Usage: "  "$(( ${data[used_metadata_blocks]} * ${data[metadata_block_size]} )) bytes"
	printf "%-*s%s\n" "30" "Metadata Usage: " "$(( 100 * ${data[used_metadata_blocks]} / ${data[total_metadata_blocks]} )) %"

else
    echo "Device not found or no valid status output."
fi