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Good suggestion, thank you. Unfortunately the machine in question is a VPS.
RAM issues are usually indicated by "bad alloc" in either the bitcoin or the systems log files.
Edit: I wrote this small bash script to see whether the high memory usage was related to the spam attack:
#!/bin/bash
date="$(date +%F-%R)" #current date and time
sizebytes="$(bitcoin-cli getmempoolinfo | grep [size,bytes] | egrep -o [0-9]*)"
usedfree="$(free -m | grep "^-/+" | egrep -o [0-9]*)"
mem=()
while read -r line; do
mem+=("$line")
done <<< "$usedfree"
#echo "${mem[0]}|${mem[1]}"
txp=()
while read -r lines; do
txp+=("$lines")
done <<< "$sizebytes"
echo "$date|${txp[0]}|${txp[1]}|${mem[0]}|${mem[1]}" >> badalloc.log
I also add a header every 24 hours.
#!/bin/bash
echo " | transactions |memory usage " >> badalloc.log
echo "yyyy-mm-dd-hh:mm|count|size in b|used|free " >> badalloc.log
echo "------------------------------------------------" >> badalloc.log
Sample output for today:
2015-10-21-00:00|3480|48161814|1014|1033
2015-10-21-00:30|4747|48826423|1005|1042
2015-10-21-01:00|4799|49154506|1011|1036
2015-10-21-01:30|3183|46341550|1010|1037
2015-10-21-02:00|3375|46089678|1009|1038
2015-10-21-02:30|5151|47420064|1007|1040
2015-10-21-03:00|3888|47239752|1007|1040
2015-10-21-03:30|3268|45954609|1008|1039
2015-10-21-04:00|3151|45941656|1007|1040
2015-10-21-04:30|5634|47096129|1012|1035
2015-10-21-05:00|3173|45684240|1011|1036
2015-10-21-05:30|3909|46216545|1013|1034
2015-10-21-06:00|3611|46493840|1014|1033
2015-10-21-06:30|2665|45533389|1012|1035
2015-10-21-07:00|2498|45544151|1013|1034
2015-10-21-07:30|3131|45766006|1013|1034
2015-10-21-08:00|2890|45569655|1012|1035
2015-10-21-08:30|2443|45245305|1012|1035
2015-10-21-09:00|2744|45360579|1014|1033
2015-10-21-09:30|5239|46643096|1013|1034
2015-10-21-10:00|2198|45117686|1010|1037
2015-10-21-10:30|2513|45267968|1013|1034
2015-10-21-11:00|2906|45545321|1015|1032
2015-10-21-11:30|5426|46894335|1013|1034
2015-10-21-12:00|3763|46400627|1013|1034
2015-10-21-12:30|3561|45821454|1014|1033
2015-10-21-13:00|2590|45319224|1013|1034
2015-10-21-13:30|5475|46684401|1012|1035
2015-10-21-14:00|3283|45402129|1014|1033
2015-10-21-14:30|3507|45459846|1014|1033
2015-10-21-15:00|2304|45251642|1012|1035
2015-10-21-15:30|3715|45973617|1014|1033
2015-10-21-16:00|4527|46787327|1017|1030
2015-10-21-16:30|2900|45193467|1014|1033
2015-10-21-17:00|4243|46137966|1014|1033
2015-10-21-17:30|3305|45609139|1014|1033
2015-10-21-18:00|3026|45826635|1013|1034
2015-10-21-18:30|4244|46093039|1014|1033
2015-10-21-19:00|3101|45242942|1014|1033
2015-10-21-19:30|6241|46563020|1014|1033
2015-10-21-20:00|4329|46195139|1012|1035
2015-10-21-20:30|5004|46176541|1013|1034