I believe a mechanism for counting pipe [under,over]runs would be useful during debug. If, during a particular workload, you consistently see X pipe underruns, and then apply a patch and see "10% less" pipe underruns, you can say you've progressed or regressed. Propose adding a quick counter every vsync. I'll post an RFC patch today or tomorrow.
Sent RFC to mailing list: * http://patchwork.freedesktop.org/series/2852/
Joe, is this issue still valid?
Closing as no response. Joe if your patch is not in and you are not happy, please re-open.
My original RFC was overly simplistic when I submitted it. And given how much development has happened over the last year, it would likely need a complete re-think and re-vamp. There is a need for accurate underrun accounting for debug, though I haven't the bandwidth to meet that need.
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