#!/bin/bash

########
# ksm-stats
# version 2023-06-09.1
#
# License CC-BY-SA 4.0
# https://wiki.tnonline.net
########


# Directory containing the KSM files
directory="/sys/kernel/mm/ksm/"

# Get system page size in bytes
page_size=$(getconf PAGESIZE)

# Declare an associative array to store variables and values
declare -A variables

# Get a list of variable files
variable_files=("$directory"/*)

# Iterate over variable files
for file in "${variable_files[@]}"; do
    # Get the variable name from the file name
    var=$(basename "$file")

	# Read the variable value from the file
    read -r value < "$file"

    # Store the variable and value in the array
    variables["$var"]="$value"
done

# Calculate the total memory used and saved by KSM in MiB
memory_used=$((variables["pages_sharing"] * page_size / (1024 * 1024) ))
memory_saved=$((memory_used - (variables["pages_shared"] * page_size / (1024 * 1024)) ))

# Calculate the efficiency ratio
if [ "${variables["pages_shared"]}" -ne 0 ]; then
    efficiency_ratio=$(bc <<< "scale=2; ${variables["pages_sharing"]} / ${variables["pages_shared"]}")
else
    efficiency_ratio=0
fi

# Determine the maximum length of variable names
# This is used to set column widths.
max_length=0
for var in "${!variables[@]}"; do
	if [ ${#var} -gt $max_length ]; then
		max_length=${#var}
	fi
done
((width = max_length + 4))

# Iterate over variables and output their names and values
printf "========\n"
printf "SETTINGS"
printf "\n========\n"

for var in "${!variables[@]}"; do
	# Get the variable value from the array
    value=${variables["$var"]}

	# Output the variable name and value in columns
	printf "%-*s%s\n" "$width" "$var" "$value"
done

# Output the total memory used, memory saved and efficiency ratio.
printf "\n========\n"
printf "SUMMARY"
printf "\n========\n"
printf "%-*s%s MiB\n" "$width" "Total Memory Used by KSM:"  "$memory_used"
printf "%-*s%s MiB\n" "$width" "Total Memory Saved by KSM:" "$memory_saved"
printf "%-*s%s\n"     "$width" "Efficiency Ratio:"          "$efficiency_ratio"