Like I mentioned in my previous post , Today I am going to exploring TPL ETW traces. Yes, I know we could use the built in VS.NET profiler, but in production environment we don’t have VS.NET and guess what even VS.NET parallel profiler uses only ETW to get those good looking graphs.
With the today’s release of source code from BCL, I am going to be using PerfMonitor to parse these traces and dump them out in xml file. TPL uses ‘self-manifests’ (The manifest is dumped as event data) we don’t need a man file to interpret it (since it is in the stream). The TraceEvent code has the ability to decode these events using the manifest in the data stream.
The sample I am going to be using for tracing is MandelbrotFractals_CSharp which is from the PFX Team
I am starting the trace using xperf , on the TPL ETW provider
xperf -start clr -on 2e5dba47-a3d2-4d16-8ee0-6671ffdcd7b5 -f clrevents.etl
Started the application and then stopped the trace using
xperf -stop clr
I had to make few changes to the TraceEvent Code, these are minor . Especially the code didn’t handle Boolean and it was throwing an exception , anybody can make this simple fix.
To get the trace from the ETL to xml here is the command
PerfMonitor.exe /keepETL print clrevents.etl
In the above command we are instructing the exe to convert the etl to xml and not to delete the ETL file after doing it.
The above command output’s an xml file. Here is a sample output from the actual xml file.
<Event MSec= "24181.0409" PID="1635144" PName="(1635144)" TID="1634556" EventName="TaskStarted" ProviderName="TplEtwProvider" OriginatingTaskSchedulerID="1" OriginatingTaskID="0" TaskID="5"/> <Event MSec= "24181.0734" PID="1635144" PName="(1635144)" TID="1634556" EventName="TaskScheduled" ProviderName="TplEtwProvider" OriginatingTaskSchedulerID="1" OriginatingTaskID="5" TaskID="6" CreatingTaskID="4" TaskCreationOptions="10500"/> <Event MSec= "24181.0772" PID="1635144" PName="(1635144)" TID="1634556" EventName="ParallelFork" ProviderName="TplEtwProvider" OriginatingTaskManager="1" OriginatingTaskID="5" ForkJoinContextID="1"/> <Event MSec= "24413.3543" PID="1635144" PName="(1635144)" TID="1634556" EventName="ParallelJoin" ProviderName="TplEtwProvider" OriginatingTaskSchedulerID="1" OriginatingTaskID="5" ForkJoinContextID="1"/> <Event MSec= "24413.3624" PID="1635144" PName="(1635144)" TID="1634556" EventName="TaskScheduled" ProviderName="TplEtwProvider" OriginatingTaskSchedulerID="1" OriginatingTaskID="5" TaskID="7" CreatingTaskID="4" TaskCreationOptions="10500"/> <Event MSec= "24413.3791" PID="1635144" PName="(1635144)" TID="1634556" EventName="TaskCompleted" ProviderName="TplEtwProvider" OriginatingTaskSchedulerID="1" OriginatingTaskID="0" TaskID="5" IsExceptional="False"/>
From the above we can see when the task was scheduled, which is the originating task and when did it complete.
This wouldn’t have been possible without ETW, even with Windbg we cannot these information. This can help us understand what is happening with in TPL , which will enable us to design better.
FYI, Perfmonitor is just an implementation of the TraceEvent API which converts the ETW data to xml. It gives us possibilities to extend this.
In the coming posts I will be exploring how ETW can literally replace debugger in Production environment. Don’t get me wrong, I am very BIG fan of Windbg and have been using it to understand the OS and the CLR.
Thanks to Vance Morrison for letting me know about TraceEvent.
