Flush Linux swap back to RAM, suppresses alerting in Zabbix - useless for actual performance tuning

swap-flush.sh

#!/bin/sh

test "0" = "$(grep -vc '^Filename' /proc/swaps)" && exit 0  # ..no swaps

SWAP_FREE="$(awk '
    /^SwapTotal:/    { total  = $2 }
    /^SwapFree:/     { unused = $2 }
    END { printf "%d\n", 100 * unused / total }' /proc/meminfo)"

test "$SWAP_FREE" -lt "${SWAP_NEED_FREE:-55}" || exit 0

MEM_ENOUGH="$(awk '
    /^SwapTotal:/    { total  = $2 }
    /^SwapFree:/     { unused = $2 }
    /^MemAvailable:/ { avail  = $2 }
    END { printf "%d\n", (avail > (total - unused)) }' /proc/meminfo)"

test "$MEM_ENOUGH" = "1" || {
    logger -p "user.warn" -t "${0##*/}.nomem" -- "swap free ${SWAP_FREE}%, but no memory for flush"
    exit 1
}

logger -p "user.notice" -t "${0##*/}" -- "swap free ${SWAP_FREE}%, TRY TO FLUSH"

swapoff -a 2>&1 | logger -e -p "user.err" -t "${0##*/}.swapoff"
swapon  -a 2>&1 | logger -e -p "user.err" -t "${0##*/}.swapon"

## END ##