Powershell作业未并行执行

Question

Expecting this to run in 5+ seconds (Assuming I have 4 cores and each job can run on each core).

$emailTimes =  @(0) * 4  

Write-Host "[$(Get-Date -Format HH:mm:ss.fff)] Starting"  
for ($index=0;$index -lt ($emailTimes.length); $index++) {  
  Start-Job -Name "job$index" -ScriptBlock {sleep 5}  
}  
Write-Host "[$(Get-Date -Format HH:mm:ss.fff)] Waiting"  
Get-Job | Wait-Job  
Get-Job | Receive-Job  
Write-Host "[$(Get-Date -Format HH:mm:ss.fff)] Completed"  

Answer 1

Cores do not matter, you can run 100 jobs with one core in parallel.

What i did now is:

foreach ($i in 1..10 ) { Start-Job -ScriptBlock {SLEEP -Seconds 5} }
MEASURE-COMMAND { Get-Job|Wait-Job }

and it finishes in:

TotalSeconds      : 6,2208058

Yet - running it few times, once i got:

TotalSeconds      : 14,3781632

So it can be slow, but it's definitely running in parallel

I've started checking this and I i think OP might be on to something. have started few jobs in parallel like this :

    get-job|remove-job
echo "start:"
get-date -UFormat " %H:%M:%S"
1..18| % { 
    Start-Job -ScriptBlock {
        $obj = ""|select starttime, runtime, finishtime 
        $obj.starttime = get-date -UFormat " %H:%M:%S"
        $obj.runtime = measure-command {SLEEP -Seconds 1}|select -ExpandProperty totalseconds
        $obj.finishtime = get-date -UFormat " %H:%M:%S"
        $obj
    } |out-null 

} 
echo "finished spinning up jobs at:"
get-date -UFormat " %H:%M:%S"
echo "all jobs finished at "
Get-Job|Wait-Job |out-null
get-date -UFormat " %H:%M:%S"
echo "run time of each job"

get-job|receive-job| ft

and result was like this output:

start:
 23:04:27
finished spinning up jobs at:
 23:04:31
all jobs finished at
 23:05:23
run time of each job

starttime   runtime finishtime
---------   ------- ----------
 23:05:07 1,0037849  23:05:08
 23:05:07 1,0037791  23:05:08
 23:05:22 1,0036025  23:05:23
 23:05:22 1,0040943  23:05:23
 23:05:22  1,003943  23:05:23
 23:05:22 1,0116236  23:05:23
 23:05:22 1,0217624  23:05:23
 23:05:22 1,0056518  23:05:23
 23:05:22 1,0038563  23:05:23
 23:05:22 1,0082825  23:05:23
 23:05:22 1,0042454  23:05:23
 23:05:22 1,0033923  23:05:23
 23:05:22 1,0128473  23:05:23
 23:05:22 1,0190476  23:05:23
 23:05:22 1,0188348  23:05:23
 23:05:22 1,0235496  23:05:23
 23:05:22 1,0058239  23:05:23
 23:05:22 1,0153528  23:05:23

Notice 40 second delay from script start to first job start, and 15 second break between first 2 and rest?

The more jobs run in parallel - the worse it gets. Starting 100 jobs with 10 second sleep (so that first does not finish before all are started) just hung PS window and never finished... which is weird, because i was using hundreds of jobs , each taking more than 10 seconds to finish and have never encountered such issues before.

This needs further testing of different machines (os/processor/anti-virus maybe?) and different powershell versions.

I also thought that maybe it's something specific to start-sleep function but no - have used different methods to get it running few seconds and still same effect. Have to check it because I use powershell jobs (mainly invoke-command -asjob ) daily and if this keeps like this - I might need to consider switching to runspaces or workflows for my parallel processing needs...