Windows PsApi GetPerformanceInfo C# Wrapper

I was allways interested in digging into windows internals, in the time I was just working on Top Process when saw this question on Stack Overflow.

And after answering that I put togher little class forWindows PsApi function GetPerformanceInfo. It's easyer to use than answer on SO, with it you can get information about memory, process count, handles count etc.

Download (c# source file):

Usage sample :
PerfomanceInfoData perfData = PsApiWrapper.GetPerformanceInfo();
Console.Write("Available memory: " + perfData.PhysicalAvailableBytes.ToString());
Console.Write("Total memory: " + perfData.PhysicalTotalBytes.ToString());

Here is the code :
  public class PerfomanceInfoData
      public Int64 CommitTotalPages;
      public Int64 CommitLimitPages;
      public Int64 CommitPeakPages;
      public Int64 PhysicalTotalBytes;
      public Int64 PhysicalAvailableBytes;
      public Int64 SystemCacheBytes;
      public Int64 KernelTotalBytes;
      public Int64 KernelPagedBytes;
      public Int64 KernelNonPagedBytes;
      public Int64 PageSizeBytes;
      public int HandlesCount;
      public int ProcessCount;
      public int ThreadCount;

  public static class PsApiWrapper
    [DllImport("psapi.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool GetPerformanceInfo([Out] out PsApiPerformanceInformation PerformanceInformation, [In] int Size);

    public struct PsApiPerformanceInformation
      public int Size;
      public IntPtr CommitTotal;
      public IntPtr CommitLimit;
      public IntPtr CommitPeak;
      public IntPtr PhysicalTotal;
      public IntPtr PhysicalAvailable;
      public IntPtr SystemCache;
      public IntPtr KernelTotal;
      public IntPtr KernelPaged;
      public IntPtr KernelNonPaged;
      public IntPtr PageSize;
      public int HandlesCount;
      public int ProcessCount;
      public int ThreadCount;

    public static PerfomanceInfoData GetPerformanceInfo()
      PerfomanceInfoData data = new PerfomanceInfoData();
      PsApiPerformanceInformation perfInfo = new PsApiPerformanceInformation();
      if (GetPerformanceInfo(out perfInfo, Marshal.SizeOf(perfInfo)))
        /// data in pages
        data.CommitTotalPages = perfInfo.CommitTotal.ToInt64();
        data.CommitLimitPages = perfInfo.CommitLimit.ToInt64();
        data.CommitPeakPages = perfInfo.CommitPeak.ToInt64();

        /// data in bytes
        Int64 pageSize = perfInfo.PageSize.ToInt64();
        data.PhysicalTotalBytes = perfInfo.PhysicalTotal.ToInt64() * pageSize;
        data.PhysicalAvailableBytes = perfInfo.PhysicalAvailable.ToInt64() * pageSize;
        data.SystemCacheBytes = perfInfo.SystemCache.ToInt64() * pageSize;
        data.KernelTotalBytes = perfInfo.KernelTotal.ToInt64() * pageSize;
        data.KernelPagedBytes = perfInfo.KernelPaged.ToInt64() * pageSize;
        data.KernelNonPagedBytes = perfInfo.KernelNonPaged.ToInt64() * pageSize;
        data.PageSizeBytes = pageSize;

        /// counters
        data.HandlesCount = perfInfo.HandlesCount;
        data.ProcessCount = perfInfo.ProcessCount;
        data.ThreadCount = perfInfo.ThreadCount;
      return data;