Huge memory use from small powershell script

Question

I have this script to trap the IP's on a network to compare to historic packet captures as part of a larger problem solving exercise.

function qp($comp)
    {
    $p = ping $comp -n 1 -w 2 -4
    IF($? -eq $true){$out = $p[1].split("[")[1].split("]")[0]}
    else{$out = $False}
    return $out
    }

$comps = Get-Content C:\PacketCapture\comps.txt

DO
    {
    foreach($comp in $comps)
        {
        ECHO "$(qp $comp);$comp" >>"C:\PacketCapture\IP_$(Get-date -format HHmm-ddMMyy).txt"
        }
    Start-sleep 3600
    }
until($null -eq "WANG")

I set this off initially a fortnight ago, at the middle of last week the terminal it was running on was grinding to a halt as the memory use for the power shell process was nearly at 2GB.

I stopped and restarted it and again we were at 1.2GB RAM use this morning.

Whilst not particularly critical, I've modified this to run once then stop/start itself, I'm interested to know which element is causing the memory leak and how I would identify that in the future.

I could see it being worse but have you tried using Test-Connnection -Quiet? It would remove the need for string manipulation although that should finish rather quickly. Also what PowerShell version are you running this with. — Matt
– Matt, Commented Oct 5, 2015 at 12:07
First, how large is comps.txt? Second, why even use ping.exe when there's Test-Connection cmdlet? Finally, your do..until is funny but while ($true) { ... } is more common. — Alexander Obersht
– Alexander Obersht, Commented Oct 5, 2015 at 12:11
I agree with the others about using Test-Connection. That said, what if you sprinkled in a [GC]::Collect(), maybe in the look after the Start-Sleep? Just curious if that helps. — briantist
– briantist, Commented Oct 5, 2015 at 12:35
Try VMMap from sysinternals. It allows you to view the memory usage pattern of a process over time. When at 1.2GB ram, you could take a memory dump using procdump (or procexp or taskmanager -> right click -> create dumpfile) and analyze it with WinDbg. — Lieven Keersmaekers
– Lieven Keersmaekers, Commented Oct 5, 2015 at 14:35
fwiw - I didn't notice any memory drain/leak when running this on my computer with the Start-Sleep removed. — Lieven Keersmaekers
– Lieven Keersmaekers, Commented Oct 5, 2015 at 14:36

briantist · Accepted Answer · 2015-10-05 18:13:35Z

2

You could try invoking garbage collection manually. I think the do/until loop is a good place for it:

DO
    {
    foreach($comp in $comps)
        {
        ECHO "$(qp $comp);$comp" >>"C:\PacketCapture\IP_$(Get-date -format HHmm-ddMMyy).txt"
        }
    Start-sleep 3600
    [GC]::Collect()
    }
until($null -eq "WANG")

edited Oct 5, 2015 at 18:13

answered Oct 5, 2015 at 15:57

briantist

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sodawillow · Accepted Answer · 2015-10-05 17:43:41Z

-1

Try introducing garbage collection into your code with [System.GC]::Collect()

Source : https://dmitrysotnikov.wordpress.com/2012/02/24/freeing-up-memory-in-powershell-using-garbage-collector

edited Oct 5, 2015 at 17:43

sodawillow

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answered Oct 5, 2015 at 15:07

Jimbo

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8 Comments

Matt Over a year ago

You should actually include the code from the link... its one line. This is a poor answer without it.

Matt Over a year ago

It is the right answer but what happens when the link dies? This is a link-only answer right now which is discouraged at SO. My comment is not poor. It is an attempt at constructive criticism.

Matt Over a year ago

But users wouldn't have to bother finding anything if you wrote the 15 characters in the answer and kept the link for context is my point.

Patrick Over a year ago

Jimbo thanks for the answer, Matt is technically correct. Stack Overflow prefer you include the crux of your answer here and not just via a link. However @Matt, Stack Overflow is collaborative, feel free to edit Jimbo's answer to include the pertinent details.

Matt Over a year ago

@Patrick I am aware of that yes. I was taking the teach a man to fish approach.

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