Dan McKinley
Math, Programming, and Minority Reports

    #
    # trim-perflog.msh
    #   This pares down a set of enormous perfmon logs to a
    #   size that can be managed by the Microsoft LogParser.
    #
    #   This finds the column indices that we're interested in,
    #   then runs through each line in the input CSV file(s)
    #   and pulls them out.
    #
    
    # The counters in the perfmon trace that we're interested in.
    #
    $counters =
    "(PDH-CSV 4.0) (Eastern Standard Time)(300)",
    "\\machine\.NET CLR Exceptions(w3wp)\# of Exceps Thrown / sec",
    "\\machine\.NET CLR LocksAndThreads(w3wp)\Contention Rate / sec",
    "\\machine\.NET CLR Memory(w3wp)\% Time in GC",
    "\\machine\.NET CLR Remoting(w3wp)\Remote Calls/sec",
    "\\machine\Process(w3wp)\Page Faults/sec",
    "\\machine\Process(w3wp)\% Processor Time",
    "\\machine\Process(w3wp)\% User Time",
    "\\machine\Process(w3wp)\% Privileged Time",
    "\\machine\Process(w3wp)\Private Bytes";
    
    # Prettier names for the counters.
    #
    $columnAlias = "time", "exceptionsPerSecond",
    "contentionPerSecond", "pctTimeInGC",
    "remoteCallsPerSecond", "pageFaultsPerSecond",
    "pctProcessorTime", "pctUserTime",
    "pctPrivelegedTime", "privateBytes";
    
    # Returns an array that contains the index of each of the
    # $counters in the csv.
    #
    function getPerflogIndices
    {
        param([System.String]$columns)
    
        $tokens = $columns.Split(',');
        for($i = 0; $i -lt $tokens.Length; $i++)
        {
            $t = $tokens[$i];
            $t = $t.Substring(1, $t.Length-2);
            $index = -1 ;
            for($j = 0; $j -lt $counters.Length; $j++)
            {
                if($t -eq $counters[$j])
                {
                    $index = $j;
                }
            }
            if($index -ge 0)
            {
                write-object $i;
            }
        }
    }
    
    # writes a CSV line using the values in $array.
    #
    function write-array
    {
        param([System.IO.StreamWriter]$writer, $array)
        $j = 0;
        $last = $array.Length;
        foreach($a in $array)
        {
            $writer.Write($a);
            if($j -ne $last)
            {
                $writer.Write(",");
            }
            $j++;
        }
        $writer.WriteLine();
    }
    
    # Writes a single line to the result CSV file.
    # This requires:
    #    $writer  - The output stream.
    #    $ln      - A single line read from
    #                the input stream.
    #    $indices - The column indices of the
    #                  subject perfmon counters.
    #
    function write-csv-line
    {
        param([System.IO.StreamWriter]$writer,
           [System.String]$ln, [System.Object[]]$indices)
    
        $vals = $ln.Split(',');
        $j = 0;
        $last = $indices.Length - 1;
        foreach($i in $indices)
        {
            $writer.Write($vals[$i]);
            if($j -ne $last)
            {
                $writer.Write(",");
            }
            $j++;
        }
        $writer.WriteLine();
    }
    
    # Trims down the input CSV file. If $names is True,
    # writes the names of the columns as the first line
    # in the output.
    function trim-perflog
    {
        param([System.IO.FileInfo]$in, [System.Boolean]$names)
    
        $r = $in.OpenText();
        $ln = $r.ReadLine();
        $indices = getPerfLogIndices $ln;
    
        $wr = [System.IO.File]::AppendText($out);
        if($names)
        {
            write-array $wr $columnAlias;
        }
        while($r.Peek() -ge 0)
        {
            write-csv-line $wr $r.ReadLine() $indices;
        }
        $wr.Close();
    }
    
    $out = "c:\perflogs\output.csv";
    
    trim-perflog c:\perflogs\prod_000005.csv True
    trim-perflog c:\perflogs\prod_000006.csv False
    trim-perflog c:\perflogs\prod_000007.csv False