A Real-Time Per-Thread/Task Perf Stats Tracker #43610

AB#1244363

Background and Motivation

In Bing, we want to track performance of dynamically loaded plugin code very closely so that we can figure out whether the code is staying within the bounds of good performance and behavior. A plugin that gets too far out of bounds can be disabled or run at a lower priority, for example.

Currently, we can track the following in real-time:

• Wall-time (Stopwatch)
• CPU-time (Win32 API GetThreadTimes)
• Unhandled exceptions

In addition, we can track the following with ETW events, but only after the fact, or in limited-time profiles.

• Memory allocation (especially LOH allocations)
• First-chance exceptions
• JITted methods

We'd like to be able to get these stats via API, in order of importance:

1. GC - Bytes Allocated (GC.GetAllocatedBytesForCurrentThread appears to satisfy this)
2. JIT stats - % time (CPU time? wall time?)
   a. Jitted bytes would be nice to have here, but time is more important.
3. Locks taken, # of times thread was blocked
4. Exceptions thrown - aware that we can listen to FirstChanceException handler, but this process-global, as far as I know, so messier to deal with.

Proposed API and Example

We could wrap the stats in a Stopwatch like class that gets a lot more than time:

var mon = new ThreadStatsMonitor();
mon.Start()

thirdPartyCode.Execute();

mon.Stop();

Logger.Log(
  mon.BytesAllocated, // I'm aware of GC.GetAllocatedBytesForCurrentThread
  mon.JITCPUTime,
  mon.MethodsJitted,
  mon.ILBytesJited, 
  mon.nativeBytesGenerated,
  mon.ExceptionsThrown, //i.e., first-chance exceptions
  mon.LockSynchronizations, 
  mon.CPUTime, 
  mon.WallTime,
);

// This is simplistic logic, but conveys the point
if (mon.BytesAllocated > MaxBytesPerPlugin)
{
  thirdPartyCode.Disable();  
}

Risks

Pay-for-play. Not everybody wants all the stats. Some of the stats could be expensive to generate.