Optimize the startup of powershell sessions #174
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Before doing this, a powershell session takes around 6s to begin on an n1-standard-4, over winrm Afterwards, on the order of 200ms For us, using winrm as the packer/ansible communicator, this reduced provisioning time from around 25m to around 8m Not sure if this is the place to call it, compared to it happening inside an on-boot scheduled task; happy to move it, obviously.
sysprep/instance_setup.ps1
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| if (! $_.location) {continue} | ||
| $Name = Split-Path $_.location -leaf | ||
| if ($Name.startswith("Microsoft.PowerShell.")) { | ||
| Write-Progress -Activity "Native Image Installation" -Status "$name" |
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Write-Progress can cause issues when there is no console attached (as is the case here), if you want this stuff printed out you can use the Write-Log function
sysprep/instance_setup.ps1
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| @@ -287,6 +305,7 @@ else { | |||
| Write-Log 'Running startup scripts from metadata server.' | |||
| Create-GCEStartup | |||
| Invoke-ExternalCommand schtasks /run /tn GCEStartup | |||
| Optimize-PowershellAssemblies | |||
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Whats' the time for this to run, since this isn't required for instance setup it would make more sense to add before Wait-Job (if its <2s) or after if greater. you could also start it in the background if that makes more sense.
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On an n1-standard-4 I've seen this take around 30s. I've moved this down to just after Wait-Job - is that what you meant?
sysprep/instance_setup.ps1
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| @@ -245,6 +245,24 @@ function Create-GCEStartup { | |||
| $folder.RegisterTaskDefinition('GCEStartup',$task,6,'System',$null,5) | Out-Null | |||
| } | |||
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| function Optimize-PowershellAssemblies { | |||
| # NGEN powershell assembly, improves startup time of powershell by 10x | |||
| $old_path = $env:path | |||
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This is pretty aggressive, do you have to overwrite the path? This only really matters if you run this function in the background.
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No, that was just simplest. I've adjusted.
don't brutalise the PATH; move the call later in the sequence
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I'm holding off on this for now as I am looking into other ways to handle this. If nothing pans out I'll come back to this PR. |
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Please test out the latest images, this change should be in the base image build now and initial startup time should have actually gone down as a result. |
Before doing this, a powershell session takes around 6s to begin on an n1-standard-4, over winrm. Afterwards, on the order of 200ms.
For us, using winrm as the packer/ansible communicator, this reduced provisioning time from around 25m to around 8m.
Not sure if this is the place to call it, compared to it happening inside an on-boot scheduled task; happy to move it, obviously.
All credit to @ca-johnson for actually finding this optimisation after an extended session of profiling!
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