Gen 0 GC over-allocation issue in AB Testing

Description

It’s caused by the IsInSystemFolder method of the TestingContextHelper class.

public bool IsInSystemFolder()
    {
bool flag = true;
if (this._contextHelper.HasCurrentContext())
        flag = this._contextHelper.RequestedUrl().ToLower().Contains(this._episerverHelper.GetRootPath().ToLower());
return flag;
    }

If you notice the blue underlines above, you’ll see that this method is called within a RaiseContentEvent repeatedly within an individual request. The number of calls to this method is dependent on the volume of content being loaded, consequently.

This method calls RequestedUrl() and performs a ToLower() method on the resulting string. It does the same for GetRootPath().
You can see on the right side of perf view that these result in a large amount of memory being allocated because the multiplier is called per piece of content being loaded.
Overall, this one method is allocating 146MB of memory to Gen 0 within a 130 second timeframe. Based on an average of 3 pieces of content being loaded, we could reduce this one method’s allocations by 2/3 (or 97MB in 130 seconds) by simply storing the lowered string value within the _contextHelper and episerver helper. If there were 100 pieces of content being loaded, the reduction would be 99/100ths, and so on.