ksm

#!/sbin/openrc-run

readonly ksm_dir=/sys/kernel/mm/ksm
readonly ksm_pages_sharing=${ksm_dir}/pages_sharing
readonly ksm_pages_to_scan=${ksm_dir}/pages_to_scan
readonly ksm_run=${ksm_dir}/run
readonly not_supported="Kernel does not support Kernel Samepage Merging"
readonly page_size=$(getconf PAGESIZE)

btoh() {
    awk '{
        if ($1 == 1) {
            print "1 byte"
        } else {
            split("bytes KiB MiB GiB TiB PiB EiB ZiB YiB", suffix)
            for (power = 1; $1 > 1024; power++) {
                $1 /= 1024
            }
            if ( power > 1 ) {
                format = "%.2f %s"
            } else {
                format = "%d %s"
            }
            printf(format, $1, suffix[power])
        }
    }' <<< "${1}"
}

depend() {
    before libvirtd
}

start() {
    ebegin "Starting KSM (Kernel Samepage Merging)"

    if [[ ! -f "${ksm_run}" ]]; then
        eend 1 "${not_supported}"
        return 1
    fi

    if [[ -n "${pages_to_scan}" ]]; then
        echo "${pages_to_scan}" > "${ksm_pages_to_scan}"
    fi
    echo 1 > "${ksm_run}"
    eend "${?}"
}

stop() {
    ebegin "Stopping KSM (Kernel Samepage Merging)"

    if [[ ! -f "${ksm_run}" ]]; then
        eend 1 "${not_supported}"
        return 1
    fi

    echo 0 > "${ksm_run}"
    eend "${?}"
}

status() {
    if [[ ! -f "${ksm_run}" ]]; then
        eerror "${not_supported}"
        return 1
    fi

    local run=$(cat "${ksm_run}")
    local sharing=$(cat "${ksm_pages_sharing}")
    local saved=$((sharing * page_size))
    local human=$(btoh "${saved}")
    if [[ "${run}" -eq 1 ]]; then
        einfo "KSM (Kernel Samepage Merging) is running; ${human} saved"
        return 0
    else
        einfo "KSM (Kernel Samepage Merging) is not running; ${human} saved"
        return 1
    fi
}

# Local Variables:
# mode: sh
# sh-basic-offset: 4
# indent-tabs-mode: nil
# End: