I had assumed in the past that I was just seeing a glitch in my setup when the 'test result trend' graph "went funny".
However, I have had a spate of build failures more recently that caused me to 'tidy up' and delete failed builds for which the testing simply was not relevant - and now can only see 2 or 3 builds in the trend chart. Not at all useful.
And yes, I have also seen memory issues in the past, and traced it back to the way the trendChart 'recursively' read the Junit XML logs (or rather, it looked that way from the stack trace), rather than linearly counting back the jobs, and simply culling out the necessary data. From a data processing point of view, the same amount of file reading is performed; but one is locking up data on the stack, the other has the opportunity of getting rid of data not pertinent to the job in hand [ oh, and feel free to tell me I'm nowhere near correct here; I didn't look at the code in detail, merely filled in the blanks from what I saw in the stack trace combined with a very cursory glance at the code ]
I find the 'test result trend' graph to be incredibly useful for what I do, and can't believe that it has been so compromised for so long.