Lock-free updates for HistogramSumCount

[utpilla]

Fixes #2957

Similar to #2951

Changes

• Implement lock-free updates for HistogramSumCount

Stress Test Results

I used the follow view configuration in the stress test SDK setup to provide empty bounds for the Histogram which in turn applies HistogramSumCount aggregation:

.AddView(instrumentName: "TestHistogram", new ExplicitBucketHistogramConfiguration() { Boundaries = new double[] { } })

To better understand the perf improvement, we need to look at two scenarios:

1. There is not much contention to update the same MetricPoint. This was tested by running the following in the Run method of stress test:

TestHistogram.Record(
           random.Next(MaxHistogramMeasurement),
           new("DimName1", DimensionValues[random.Next(0, ArraySize)]),
           new("DimName2", DimensionValues[random.Next(0, ArraySize)]),
           new("DimName3", DimensionValues[random.Next(0, ArraySize)]));

3. There is high contention to update the same MetricPoint. This was tested by running the following in the Run method of stress test:

TestHistogram.Record(
           random.Next(MaxHistogramMeasurement),
           new("DimName1", "DimVal1"),
           new("DimName2", "DimVal2"),
           new("DimName3", "DimVal3"));

While there is a perf improvement in both the cases, there is a substantial improvement in the second case where there is high contention to update the same MetricPoint.

For the first scenario, Loops/ second go up from ~20M to ~24M (~20% increase)
For the second scenario, Loops/second go up from ~5.8M to ~8.3M (~43% increase)

Here are the numbers for the 1st and 2nd scenario respectively:

main branch

With this PR

[cijothomas]

@utpilla could you resolve the conflicts and do combined changelog for both this and the previous one. The approach is good, and we can merge once CI is green.

[codecov]

Codecov Report

Merging #2961 (872a829) into main (cee9006) will decrease coverage by 0.03%.
The diff coverage is 75.00%.

@@            Coverage Diff             @@
##             main    #2961      +/-   ##
==========================================
- Coverage   84.01%   83.97%   -0.04%     
==========================================
  Files         254      254              
  Lines        8946     8950       +4     
==========================================
  Hits         7516     7516              
- Misses       1430     1434       +4     

Impacted Files	Coverage Δ
src/OpenTelemetry/Metrics/MetricPoint.cs	85.00% <75.00%> (-1.03%)	⬇️
...emetry.Api/Internal/OpenTelemetryApiEventSource.cs	73.52% <0.00%> (-8.83%)	⬇️
...Telemetry/Internal/SelfDiagnosticsEventListener.cs	97.65% <0.00%> (+0.78%)	⬆️

[cijothomas]

Merging. as this is doing same thing as another PR approved by all.